Technical Note - TN 024: 2015 · PDF fileshown on the standard overhead wiring footing...

Technical Note - TN 024: 2015

For queries regarding this document

[email protected] www.asa.transport.nsw.gov.au

Technical Note - TN 024: 2015 Issued date: 05 May 2015

Effective date: 05 May 2015

Subject: The use of locknuts on overhead wiring structure anchor bolts

This technical note is issued by the Asset Standards Authority as an update to RailCorp

document TMC 331 Design of Overhead Wiring Structures & Signal Gantries, Version 1.0.

1. Incorrect arrangement shown in TMC 331 Figure 65 (b) and Figure 69 (b) of TMC 331 depicts typical overhead wiring attachment

arrangements which include the use of locknuts.

AS/NZS 1252 High-strength steel bolts with associated nuts and washers for structural

engineering does not cover locknuts. They are only required in situations where the anchor

bolts are tightened to snug tight (also referred to as bolting category 8.8/S) conditions and the

baseplates are subject to vibration that could promote loosening. This is generally the situation

for overhead wiring structure anchor bolt installation.

Figure 65 (b) and Figure 69 (b) in TMC 331 are drawn in an overhead situation, illustrating the

arrangement for the locknut installed after the structural nut.

This arrangement is incorrect. The arrangement as shown in Figure 65 (b) and Figure 69 (b) of

TMC 331 shall be replaced with the requirements detailed in Section 2, and arrangement shown

in Figure 1 of this technical note.

2. New requirements For snug tight installation, the correct installation procedure is to place the locknut after the

structural washer and before the structural nut. The correct sequence of nut installation is

shown on the standard overhead wiring footing drawing, CV 0373007 250 SHS Portal Footings.

The hot dipped galvanised thin nuts to use as locknuts to suit AS/NZS 1252 assemblies for

snug tight installation shall be thin nuts in accordance with AS/NZS 1112.4 ISO metric hexagon

nuts – Chamfered thin nuts – Product grades A and B with material property Class 04 in

© State of NSW through Transport for NSW of 2

mailto:[email protected]

http://www.asa.transport.nsw.gov.au/

Technical Note - TN 024: 2015

accordance with AS 4291.2 Mechanical properties of fasteners – Nuts with specified proof load

values – Coarse thread. Figure 1 of this technical note illustrates the correct installation detail.

Figure 1 – Correct locknut details for anchor bolts drawn in usual direction

The installation procedure for locknuts on overhead wiring structure anchor bolts shall be as

follows:

i) Install the locknut after the structural washer (as per AS/NZS 1252) and finger tighten.

ii) Install the structural Class 8 (as per AS/NZS 1252) full nut after the lock-nut.

iii) Tighten the Class 8 nut while holding the locknut with an appropriate thin spanner.

iv) Continue tightening until deformation in the locknut is achieved in such a way that the

locknut thread is bearing on the lower flank of the bolt thread while the full nut is bearing on

the upper flank.

Authorisation:

Technical content prepared by

Checked and approved by

Interdisciplinary coordination checked by

Authorised for release

Signature

Name Dorothy Koukari Joe Muscat John Paff Graham Bradshaw

Position Senior Engineer Standards

A/Lead Civil Engineer A/Chief Engineer Rail Principal Manager, Network Standards and Services

© State of NSW through Transport for NSW of 2

UNCONTROLLED WHEN PRINTED Page 1 of 173

Engineering Manual Civil

TMC 331

DESIGN OF OVERHEAD WIRING STRUCTURES & SIGNAL GANTRIES

Version 1.0

Issued August 2011

Owner: Chief Engineer Civil

Approved by:

John Stapleton Principal Engineer Technology & Standards

Authorised by:

Richard Hitch Chief Engineer Civil

Disclaimer

This document was prepared for use on the RailCorp Network only. RailCorp makes no warranties, express or implied, that compliance with the contents of this document shall be sufficient to ensure safe systems or work or operation. It is the document user‘s sole responsibility to ensure that the copy of the document it is viewing is the current version of the document as in use by RailCorp. RailCorp accepts no liability whatsoever in relation to the use of this document by any party, and RailCorp excludes any liability which arises in any manner by the use of this document. Copyright

The information in this document is protected by Copyright and no part of this document may be reproduced, altered, stored or transmitted by any person without the prior consent of RailCorp.

En

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Man

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RailCorp Engineering Manual — Civil Design of Overhead Wiring Structures & Signal Gantries TMC 331

© RailCorp Page 2 of 173 Issued August 2011 UNCONTROLLED WHEN PRINTED Version 1.0

Document control

Version Date Summary of change

1.0 August, 2011 First issue

Acknowledgement The technical content of this manual was developed and written by Paul Honor, Principal Engineer Structures, Civil Design, RailCorp.



Contents

1 General ..................................................................................................................................... 7

1.1 Purpose ..................................................................................................................................... 7

1.2 How to read this Manual ........................................................................................................... 7

1.3 Engineering Authority ................................................................................................................ 7

1.4 Quality management ................................................................................................................. 7

1.5 References ................................................................................................................................ 7

1.5.1 Australian standards .................................................................................................. 7

1.5.2 RailCorp Documents .................................................................................................. 7

1.6 Design standards ...................................................................................................................... 8

2 Introduction ............................................................................................................................. 8

2.1 Overview ................................................................................................................................... 8

2.2 Definitions ................................................................................................................................. 9

3 Overhead wiring systems ....................................................................................................15

3.1 Introduction .............................................................................................................................15

3.2 Types of systems used in RailCorp ........................................................................................15

3.2.1 Fixed anchored systems ..........................................................................................15

3.2.2 Regulated systems ..................................................................................................18

3.3 Types of registration ................................................................................................................18

3.3.1 Non-independent registration ..................................................................................18

3.3.2 Independent registration ..........................................................................................18

3.4 Comparison of the systems ....................................................................................................18

3.5 Wiring combinations ................................................................................................................21

3.6 Conversion from fixed anchored systems to regulated systems ............................................21

3.7 Overlaps ..................................................................................................................................21

4 Overhead wiring structures .................................................................................................22

4.1 Structure types ........................................................................................................................22

4.1.1 Single masts ............................................................................................................22

4.1.2 Cantilever masts ......................................................................................................22

4.1.3 Portal structures .......................................................................................................23

4.1.4 Anchor structures (guyed) .......................................................................................23

4.1.5 Anchor structures (free standing) ............................................................................24

4.1.6 Walkway structures ..................................................................................................24

4.2 Drop verticals ..........................................................................................................................25

4.3 Footings ..................................................................................................................................25

4.4 Attachment to other structures ................................................................................................26

4.5 Standard drawings ..................................................................................................................27

5 Design of overhead wiring structures ................................................................................27

5.1 Design responsibility ...............................................................................................................27

5.2 Design procedures ..................................................................................................................28

5.2.1 Project stakeholder ..................................................................................................28

5.2.2 Project design process ............................................................................................29

5.2.3 Civil design process .................................................................................................30

5.2.4 Structure types - order of preference .......................................................................32



5.3 Design inputs ..........................................................................................................................33

5.4 Loadings ..................................................................................................................................34

5.4.1 Electrical loading diagrams ......................................................................................34

5.4.2 Primary load cases ..................................................................................................36

5.4.2.1 LC1 - Weight Load (WL)...........................................................................36

5.4.2.2 LC2 – Live Load (LL) ................................................................................37

5.4.2.3 LC3 – Radial Load and Anchor Load (RL) ...............................................38

5.4.2.4 LC4 – Wind Wire X (WWX) ......................................................................40

5.4.2.5 Wind loading on structure.........................................................................42

5.4.3 Combination load cases ..........................................................................................44

5.4.3.1 Strength load cases ..................................................................................44

5.4.3.2 Serviceability load cases ..........................................................................45

5.4.3.3 Stability load cases ...................................................................................45

5.5 Structural modelling ................................................................................................................46

5.5.1 Modelling techniques ...............................................................................................46

5.5.1.1 Node placement .......................................................................................46

5.5.1.2 Member releases ......................................................................................47

5.5.1.3 Section properties ....................................................................................47

5.5.2 Application of loadings .............................................................................................48

5.5.2.1 Weight load application (LC1) ..................................................................48

5.5.2.2 Live load application (LC2) .......................................................................51

5.5.2.3 Radial load and anchor load application (LC3) ........................................51

5.5.2.4 Wind load on wire application (LC4) ........................................................53

5.5.2.5 Wind load on structure application (LC5, LC6 & LC7) .............................53

5.5.3 Load combinations ...................................................................................................56

5.6 Design of structural steel members ........................................................................................56

5.6.1 Strength limit state design .......................................................................................56

5.6.1.1 Structural analysis ....................................................................................56

5.6.1.2 Steel design check ...................................................................................57

5.6.2 Serviceability limit state design ................................................................................62

5.7 Anchor configurations .............................................................................................................66

5.7.1 Fixed anchors ..........................................................................................................66

5.7.2 Moving anchors .......................................................................................................69

5.7.3 Special anchor configurations .................................................................................73

5.8 Design of footings ...................................................................................................................75

5.8.1 Standard footing design ...........................................................................................75

5.8.2 Nominated footing depth design ..............................................................................80

5.8.3 Site specific footing design ......................................................................................81

5.9 Feeder and switching structures .............................................................................................81

5.9.1 Feeder structures .....................................................................................................81

5.9.1.1 Feeder structures without access ............................................................82

5.9.1.2 Feeder structures with access .................................................................85

5.9.2 Switching structures .................................................................................................88

5.9.2.1 Mast mounted switches ............................................................................88

5.9.2.2 Switching frame ........................................................................................91

5.10 Electrical isolation ...................................................................................................................93



5.10.1 Electrical isolation by separation .............................................................................94

5.10.2 Electrical isolation using insulation material ............................................................95

5.10.2.1 Acetal copolymer (black) ..........................................................................95

5.10.2.2 HILTI HIT-Bar ...........................................................................................97

6 Design of signal gantries ...................................................................................................100

7 Assessment of existing structures ...................................................................................101

7.1 Reuse of existing structures ..................................................................................................101

7.1.1 Wire adjustments ...................................................................................................101

7.1.2 Conversion to independent registration .................................................................102

7.1.3 Conversion from fixed wiring to regulated wiring ...................................................102

7.1.4 Modifications to existing regulated wiring ..............................................................102

7.1.5 Upgrading of existing wiring system ......................................................................103

7.2 Load reduction on existing structures ...................................................................................103

7.2.1 Wind loading reduction ..........................................................................................103

7.2.2 Live load reduction .................................................................................................104

7.2.3 Longitudinal wire movement ..................................................................................104

7.3 Acceptance limit reduction ....................................................................................................107

7.3.1 Strength limit state .................................................................................................107

7.3.2 Serviceability limit state .........................................................................................107

7.4 Typical existing structure.......................................................................................................108

7.4.1 Universal column portal structures ........................................................................108

7.4.2 Cantilevered Structures .........................................................................................109

7.4.3 Parallel flange channel structures .........................................................................109

7.4.4 Rolled steel joint and broad flange beam structures .............................................110

7.4.5 Other structure configuration .................................................................................110

7.5 Condition of existing structure ...............................................................................................110

8 Documentation requirements ............................................................................................111

8.1 Documentation types ............................................................................................................111

8.2 Structure diagram drawings ..................................................................................................112

8.2.1 Structure number ...................................................................................................113

8.2.2 Structure type and size ..........................................................................................113

8.2.3 Horizontal location of mast ....................................................................................114

8.2.4 Vertical location of footing pedestal .......................................................................115

8.2.5 Bridge/boom length ................................................................................................116

8.2.6 Mast height ............................................................................................................116

8.2.7 Track centres and track names .............................................................................117

8.2.8 HTRL......................................................................................................................120

8.2.9 Drop vertical length, type and position ..................................................................121

8.2.10 Footings .................................................................................................................122

8.2.11 Features adjacent to the structure .........................................................................124

8.2.11.1 Survey cross sections ............................................................................124

8.2.11.2 Detail Survey ..........................................................................................125

8.2.12 Anchor heights .......................................................................................................125

8.2.13 Anchor plate notation .............................................................................................126

8.2.14 Guy footings ...........................................................................................................127



8.2.15 Bridge splice ..........................................................................................................129

8.2.16 Access prevention grille .........................................................................................130

8.2.17 Notes......................................................................................................................131

8.2.18 References ............................................................................................................132

8.2.19 PP/HP table ...........................................................................................................132

8.2.20 Title block ...............................................................................................................135

8.2.21 Special details ........................................................................................................137

8.2.22 Special detailing referencing multiple standard structures ....................................139

8.2.23 Multiple span portals ..............................................................................................140

8.3 Standard OHWS drawings ....................................................................................................142

8.4 Location specific detail drawings ..........................................................................................143

8.5 Documenting modifications to existing OHWS .....................................................................144

8.5.1 Line thickness and types .......................................................................................145

8.5.2 Labelling of structure and components ..................................................................145

8.5.3 Referencing of existing Structure Diagram ............................................................146

Appendix A List of standard OHWS drawings .......................................................................147

Appendix B Example structure diagram drawings ...............................................................148

Appendix C Wind loading calculations on overhead wiring ................................................151

Appendix D Wind loading calculations on standard structures ..........................................152

Appendix E Wind loading calculations on feeder cables .....................................................153

Appendix F Microstran steel design restraint values ...........................................................154

Appendix G Drop vertical position restrictions .....................................................................155



1 General

1.1 Purpose

This document specifies procedures and provides guidance for Civil Engineers in the design and documentation of structures that are required to support the overhead traction wiring and signal gantries within the RailCorp network.

It applies to all main lines, sidings and maintenance depots where overhead traction wiring and signals are installed.

1.2 How to read this Manual

This Manual should be read in conjunction with RailCorp Engineering Standard ESC 330 Overhead Wiring Structures and Signal Gantries, which defines the design standards, design loads, deflection limits and other design considerations to be applied when designing overhead wiring structures and signal gantries.

1.3 Engineering Authority

RailCorp‘s policy and procedures for technical competencies are laid out in Engineering Manual TMC 001 Civil Technical Competencies and Engineering Authority.

Design of overhead wiring structures and signal gantries may only be undertaken by persons who have been delegated the appropriate Engineering Authority.

1.4 Quality management

The Civil Designer must apply Quality Management principles when designing overhead wiring structures and signal gantries. This would typically include the use of Job and Quality Management flow charts, documentation of notes taken during field walkthroughs and documentation including identification and tracking of project clients, objectives, stakeholders, cost control, calculations and key meetings.

1.5 References

1.5.1 Australian standards

AS/NZS 1170-2002 Structural design actions

AS 1657-1992 Fixed platforms, walkways, stairway and ladders – Design, construction and installation

AS 2159-1995 Piling – Design and installation

AS 3600-2009 Concrete Structures

AS 4100-1998 Steel Structures

AS 4680-1999 Hot-dip galvanized (zinc) coatings on fabricated ferrous articles

1.5.2 RailCorp Documents

ESC 100 Civil Technical Maintenance Plan



ESC 215 Transit Space

ESC 302 Defect Limits

ESC 330 Overhead Wiring Structures and Signal Gantries

TMC 001 Civil Technical Competencies and Engineering Authority

SPC 301 Structures Construction

EP 08 00 00 01 SP Overhead Wiring Standards for the Electrification of New Routes

EP 08 00 00 16 SP Designations of Overhead Wiring Conductor Systems

EP 08 00 00 17 SP Overhead Wiring Conductor System Selection Criteria

1.6 Design standards

The civil design of overhead wiring support structures and signal gantries is to conform to RailCorp Engineering Standard ESC 330 and relevant Australian Standards and other RailCorp Standards referenced within. This Standard prescribes the design loads, deflection limits and design considerations to be applied, required clearances to tracks and standard documentation requirements.

2 Introduction

2.1 Overview

This Manual specifies procedures and provides guidance in the design and documentation of overhead wiring structures and signal gantries. It is to be read in conjunction with RailCorp‘s Design Standard ESC 330.

The Manual is constituted as follows:

Section 3 provides a brief introduction to overhead wiring systems commonly used within the RailCorp network and associated terminology. The two basic systems in use are described, viz. fixed and regulated overhead wiring systems, and the two types of support and registration, viz. independent and non-independent registration.

Section 4 introduces the different types of overhead wiring support structures in use on the RailCorp network. It gives a basic description of the major structure and footing types used within RailCorp. Minor components such as drop verticals and anchor brackets are discussed and their intended uses are also addressed. Typical sketches and photos are provided.

Section 5 details procedures and design methods to be followed when designing overhead wiring structures. The full design process required to design an overhead wiring structure is documented and it is recommended by RailCorp that these be adopted to maintain uniformity and consistency in areas such as loadings and load combinations. A common design approach will produce economical designs and allow them to be compared and reviewed quickly.

Section 6 details procedures and design methods to be followed when designing signal gantries. Signal gantries make use of some of the same structure types used for overhead wiring structures but have additional considerations such as signal cages, walkways and access ladders. As the structure is trafficable acceptable deflection limits need to be achieved.



Section 7 provides design considerations and loading reductions for assessment of existing structures. Some existing structures, when assessed using current standard requirements, do not comply as standards have developed and loadings increased. The deflection requirements specified for new structures are not always achievable when applied to existing structures. Design loading refinements to suit the particular structure under investigation are presented.

Section 8 provides documentation requirements for overhead wiring structures and signal gantries. Documentation in the form of Structure Diagrams is the major civil design output and it is critical that they contain all the relevant information presented in the correct manner. Detailed instructions and examples on RailCorp‘s Structure Diagrams requirements are provided to ensure consistency and correctness of drawings.

It is intended that this Manual be updated from time to time as required to take into account any improvements resulting from new technology, improved construction techniques, or client feedback.

2.2 Definitions

The definitions provided cover the basic terminology used in overhead wiring structure and signal gantry design. Definitions have been kept brief but many terms are explained in greater detail in other chapters of this manual.

GENERAL: OHW Overhead wiring OHWS Overhead wiring structure Electrical Designer

Person or organisation tasked to design the electrical components of an overhead wiring project, and having the necessary experience and engineering authority to do so.

Civil Design Engineer

Person tasked to design the civil/structural components of an overhead wiring project, and having the necessary experience and engineering authority to do so.

ELECTRICAL TERMS:

Airgap An overlap that is configured for feeding to both wire runs (―Feeding Airgap‖).

Auxiliary feeder An extra wire running parallel to the main OHW, which is added to enhance current-carrying capacity to supply trains.

Bay length Distance between two consecutive overhead wiring structures supporting a particular run of wiring.

Blowout The amount that the contact wire displaces, from the super elevated centreline of track at the middle of a bay length, from its straight line condition under design cross wind action.

C-calc Cantilever calculation. A RailCorp software program, used by the electrical designer, which determines (based on wiring system, surveyed track & structure data, etc) the dimensions and other details of all the fittings that make up a particular cantilever for subsequent construction.

Cantilever An assembly of fittings that supports and registers the wiring in a regulated system and pivots to allow along-track wire movement with temperature. The cantilever is attached to a mast or drop vertical. Not to be confused with the structure type 'cantilever mast'.

Catenary wire The catenary wire is a multi-strand copper conductor and is located above the contact wire. It adopts a parabolic shape determined by the distance between supports, weight carried



and cable tension. The catenary wire supports the contact wire at a flat or near flat profile for smooth pantograph running. May be used as single wire or in pairs (twin catenary).

Contact wire Solid copper wire which supplies electrical power directly to the train via contact with the train's pantographs. May be used as single wire or in pairs (twin contact). Supported by droppers from the catenary above it. The dropper grips the contact wire via two notched groves that run along the top of the wire.

Dropper Droppers are vertical lengths of solid copper wire spaced at regular intervals (typically 7m), which connect between the contact and the catenary wires in a bay of OHW. Droppers support the weight of the contact wire and set the flat slope.

Feeder Conducting cable of high current capacity which either feeds external power to the wiring system (at airgaps) or connects between wires to keep them at the same electrical potential.

Fixed anchor A fixed anchor terminates the OHW conductors and provides a means of preventing them form moving under applied tension.

Fixed anchored OHW

Fixed anchored OHW is where the conductors are directly anchored at the extremes of the wire run. Conductor heights are influenced by temperature which generally leads to poor pantograph performance at speed, particularly in extreme temperature conditions.

Fixed mid-point anchor

At a fixed mid-point anchor the catenary and contact wires are prevent from moving in the along track direction. It is used in a regulated OHW system and is located near the middle of a wire run. Tensioning of the wires is undertaken at both ends of the wire run with the fixed mid-point preventing drifting of the conductors due to out of balance loads.

In-running contact

A contact wire that is located at such a height as to allow the train pantographs to run on it and collects electrical current.

In-span feeder In-span feeders appear typically as a helical ―coil‖ in each bay of OHW between the catenary and contact wires. In-span feeders provide a means of transferring heavy current from the caterary to the contact wire(s), thus reducing current feeding through the droppers.

Moving anchor An anchor point where the OHW conductor extension or contraction is provide in response to temperature change while maintaining a constant and relatively accurate tension. Regulated tension is achieved by using a set number of appropriately sized weights that move up and down beside the anchor mast in response to change in total conductor wire length.

Out-of-running contact

Describes any section of contact wire where the train's pantograph cannot run along, usually because the wire has moved up in an overlap or gone off to anchor.

Overlap An overlap has two sets of parallel OHW conductors above each track, horizontally spaced about 300mm apart and located in one or more adjacent bays. Overlaps are configured to allow one set of conductors to end and another to begin, and in doing so provide a continuous, uninterrupted path for train pantographs to collect heavy electrical current at speed.

Overlap bay The OHW bay (or bays) over which one in-running contact wire gradually rises to become out-of-running, as the contact wire from the adjacent run lowers from out-of-running to in-running.

Overlap length The portion of the overlap bay where both sets of wires are



considered to be in-running together. Pantograph The device on top of an electric train which draws power from

the overhead wiring. It slides along the contact wire, and is as wide as possible to allow for variability in the positions of wire (with wind), track and rolling stock.

Pantograph security

Assurance that the contact wire is designed to always remain on the train pantograph, within defined limits, taking into account track curvature and high wind situations.

Pull-off arm A horizontal ―arm-shaped‖ steel fitting, used in a cantilever and in other arrangements, which holds the contact wire in the horizontal position.

Registration Lateral positioning of the contact wire in its intended alignment above the track.

Regulated OHW

Regulated OHW is where the conductors are tensioned in a manner that keeps the individual conductor tension constant. The conductors maintain their heights above track, irrespective of conductor temperature, and this leads to good pantograph performance at high speed. Tensioning is provided by means of weights and pulleys.

Sag In a bay, the height difference of the catenary between its adjacent supports and its mid point.

Stagger At a support, the intended offset of the contact wire away from the (superelevated) track centreline. Stagger is used: on curved track, to reduce what would otherwise be a large mid-bay offset (in the opposite direction); on straight track, using staggers of alternating direction at consecutive structures, to create a side-to-side travel of the contact wire on the pantograph as the train moves along, thus spreading the wear across the pantograph contact surfaces (carbon strips).

System depth For a particular wiring system, the typical maximum vertical distance (which occurs at the supports) between the catenary and contact wires. Regulated systems tend to need less system depth than fixed anchored systems, resulting in reduced structure heights.

Tension length In a regulated system, the length of wiring between a particular fixed end (or fixed mid-point) and moving end. This length of wiring is kept at a constant tension (apart from any minor tension losses along the length) by the tension regulator (setoff weights) at the moving end.

Tension regulator

Arrangement of weight stacks and pulleys at a moving end which applies a specified constant tension to the OHW conductors regardless of temperature.

Wire run Single physical length of wiring, which may be the same as the tension length (up to 1000m) or encompass two tension lengths (up to 2000m) if there is a fixed mid-point.

CIVIL TERMS:

Access prevention grille

A fabricated grille attached to masts or bridges of structures to prevent access to above the track by unauthorised individuals.

Anchor bracket Fabricated steel item attached to a rock face, bridge, concourse or any other large structure to which overhead wire can be terminated or guy rod anchored.

Anchor plate Fabricated steel item attached to the mast of a structure used to terminate the fixed or moving end of a wire run.



Anchor structure

Any overhead wiring structure that overhead wiring conductor runs are terminated on.

Boom The horizontal structural member of a cantilever mast structure. Bridge The horizontal structural member spanning between the masts

of a portal. Camber A hogging deflection built into the bridge of a long span portal

and booms of all cantilever masts to compensate for large sagging deflections when under load.

Cantilever mast Cantilever mast is the general term given to a structure consisting of a mast, boom and knee brace. The given names for standard structure such as '305SHS Light Cantilever Mast' do not specify any particular member of the structure but only refer to a specific standard structure type. In this particular structure the word 'light' indicates that the boom uses a smaller section size than the mast.

Combined structure

A structure that acts both as an overhead wiring structure and a signal gantry.

Coordinates Easting and Northing, in ISG or MGA, are used to set out overhead wiring structures. The easting and northing provided on a Structure Diagram is the centre of the mast for the structure specified, not necessarily the footing. When easting and northing is specified for a guy footing they are to the centre of the anchor lug pedestal.

Cross section Survey cross sections at the proposed location of an overhead wiring structure picking up all existing ground line feature and service. The cross section must show track centres, rail heights and superelevation based on the design alignments.

Double channel portal

Double channel portal is the general term given to a portal structure with masts and bridge consisting of fabricated section using two parallel flange channels (PFC) spaced apart with batten plates and diaphragms to form larger sections.

Double universal beam portal

Double universal beam portal is the general term given to a portal structure with masts and bridge consisting of fabricated section using two universal beams (UB) spaced apart with batten plates and diaphragms to form larger sections.

Drilling types Three standard drilling types are used for attachment of anchor plates to the majority of anchor structures. Each drilling type has a specified configuration of holes and spacing and is for a particular anchor type. D1 drilling is for fixed ends or twin weight stacks at a moving end, D2 drilling is for a single weight stack and D3 drilling is used for auxiliary catenary system which is used west of Penrith.

Drop vertical Vertical steel section (usually 150UC37) attached to the bridge or boom of an overhead wiring structure used to support electrical fittings that support and register the wiring for a track(s). Formerly referred to as a ―dropper‖ within the civil discipline.

Effective footing depth

Design depth of footing that is sufficient to provide stability to the structure. In sloped situations the effective depth is measured below the point where 2 meters of horizontal fill exists between centreline of footing and the sloped surface.

Feeder structure

An overhead wiring structure used to provide support to cabling and electrical equipment that provides additional power to the overhead wiring system.

Footing in rock A footing for an overhead wiring structure that consists of a



pedestal only anchored by reinforcing bars into sound rock. FSAM Free Standing Anchor Mast. Anchor structure consisting of a

universal column section orientated in the strong direction to align with the anchored wire. The mast is free standing, which means it is not supported by a guy rod anchored to a guy footing.

FSAM - boxed Anchor structure consisting of a universal column section which has been plated on the open sides to increase the strength. The UC section is orientated in the weak direction as the flanges of the section are used to attach moving anchor plates. The mast is free standing.

Guy footing A footing that is used as an anchor point for the guy rod to transfer wire termination loads into the ground. Also called guy block, anchor block, sometimes just 'guy' as in 'G2 guy'.

Guy rod An electrical fitting consisting of steel rod with turnbuckle used to connect the anchor plate on the structure to the guy footing. Also commonly called a ‗guy‘.

HP mast General term given to a single mast consisting of a universal column (UC) with a welded base plate that is attached to a footing via holding down bolts. HP2 mast being a 250UC73 section and HP3 mast being a 310UC97 section.

HTRL The rail level of the highest track (HTRL) being serviced by the PP, HP, Portal, Cantilever Mast or FSAM.

Kneebrace Diagonal member in a portal or cantilever mast which strengthens the knee connection between mast and bridge/boom. The kneebrace allows a lighter knee connection and smaller section sizes to be used.

Loading diagram

Electrical Loading Diagrams are produced by the electrical designer for each structure location. They contain both graphical and tabulated information relevant to the numbered attachment points giving weight loads, radial loads, wire wind loads and anchor loads. Heights above rail level for each loading are given with the datum to the track the wiring is above or reference track for anchors.

Mast Mast is the general term given to the vertical component of an overhead wiring structure and is found in portals, cantilevers and single structures. Masts of portals are also commonly called portal 'legs'.

Mid point structure

Any structure located at the mid-point of a wire run where the wiring is tensioned in both directions from that structure. Mid-point structures have additional loading conditions that need to be considered during design.

Pile footing Pile footings consist of an augured hole into which a reinforcing cage is placed and a pedestal containing the hold down bolts for the structure is placed on top. The footing is completed by pouring concrete to form a monolithic structure. A casing may be required due to boulders, sometimes referred to as 'goulies', or loose sand present in the foundation material that requires to be contained.

Pedestal The pedestal is the exposed component of the footing that contains the hold down bolt arrangement and transfers the mast loading into the structure footing e.g. pile or regular. Also sometimes called 'top box', a term which is not prefered.

PP mast General term given to a single mast consisting of a universal column (UC) placed or ―potted‖ in an augured hole and secured



with concrete. PP2 mast being a 250UC73 section and PP3 mast being a 310UC97 section. The term 'PPs' is also commonly used to describe all single masts, both PP & HP with construction to choose on site which is suitable. Hence 'PP/HP' on Structure Diagram.

PP/HP table When a project has a large number of single masts in the form of PPs and HPs then it becomes efficient to document these locations in tabulated form. A PP/HP table displays in tabulated form all the information for a single mast without the need for an individual Structure Diagram.

Portal The general term for a structure consisting of two masts with a bridge spanning between and usually has a kneebrace to provide rigidity at each mast/bridge knee connection. The std portal names such as '250SHS Portal' do not specify any particular member of the structure but refer to a specific standard structure type. The standard drawing for the structure type specifies all member sizes.

Rail level The term ―rail level‖ has a precise definition. For a given track at a given location, it is the level of the top surface of the chosen rail, where the chosen rail is: on straight track, the down rail; on curved track, the inner rail (which, for existing track, is not necessarily the low rail).

Rake Rake is the amount of slope placed on masts that are sensitive to deflection. Sloping the mast away from the direction of the load allows additional deflection to occur before the limits are exceeded. Rake is applied to PP masts, Cantilever masts and FSAMs.

Reference track

The track, named in the loading diagram, from which anchor heights are referenced.

Regular footing A large reinforced excavated footing to provide adequate structure stability with an above-ground pedestal containing the hold down bolts.

Rock socket The amount of embedment into sound rock required to provide adequate structure stability for a pile or regular footing. Not to be confused with the term ―footing in rock‖.

Signal cage A fabricated steel component that is cantilevered from a signal gantry and is used to mount signaling equipment. The signal cage also provides access to allow the equipment to be maintained.

Signal gantry A portal or cantilever structure spanning over tracks to provide support and access to signals that are required between tracks where insufficient track centres prevent the use of a standard signal post. Signal gantries usually carry signal cages, walkways and access ladders. Also called 'signal structure', a term that covers cantilever masts carrying signals.

Splice Portal bridges over 20.5 m in length are required to be fabricated in two parts to facilitate transport and galvanising. The bridge is joined in the field using a splice. The splice is usually located at a point on the bridge that has low moment.

Structure diagram

Overhead wiring structures are documented with a Structure Diagram for each location to convey the design intent to the construction phase of the project. A Structure Diagram consists of a number of elements that combine to provide a unique set of information that describes the structure required.



Structure diagram drawing

A Structure Diagram drawing is a conventional drawing sheet containing one or more Structure Diagrams. Using a scale of 1:100, Structure Diagrams are placed on the drawing sheet in order of increasing structure number. Notes, references and other relevant information are also included.

Structure number

Structure identification number assigned by the electrical designer. Letters indicate the line (e.g. NS = North Shore line). Numbers indicate roughly the distance in metres (after removing the '+' sign) from Central Station. The structure number is for identification only, not to be used to position a new structure or set out the footings.

3 Overhead wiring systems

3.1 Introduction

Electric trains within the RailCorp network operate on 1500 volt DC power. They obtain their power from the overhead wiring via their pantographs, which slide along the contact wire and maintain direct contact with it. The contact wire is installed at a specified height above the rail level. It is suspended using droppers from the catenary cable above it. The contact wire and the catenary are at the same electrical potential, and together they carry the current required to power trains.

3.2 Types of systems used in RailCorp

RailCorp uses two basic overhead wiring systems, these are:

Fixed anchored system; Regulated system.

The main difference between the two systems is in the way the wiring is anchored and tensioned. Loading diagrams for these systems will be different and this may influence the design of the supporting structures.

RailCorp Electrical Standard EP 08 00 00 16 SP provides a summary of the various fixed anchored and regulated wiring configurations.

RailCorp Electrical Standard EP 08 00 00 17 SP provides the selection criteria that are applied when planning a new line or upgrading an existing system.

RailCorp Electrical Standard EP 08 00 00 01 SP prescribes overhead wiring standards to be applied for the electrification of new routes.

The various systems and combinations are described in the following paragraphs.

3.2.1 Fixed anchored systems

In a fixed anchored system both ends of the wiring length (typically up to 2 or 3 km) are fixed rigidly to an anchor structure. At supporting structures in between, the catenary is generally supported from the bridge of the structure by means of a hanger wire. The contact wire and catenary are restrained laterally by span wires. A typical support structure is illustrated in Figure 2. If the temperature of the system increases the wiring will sag between structures. The wiring does not normally move longitudinally.

In curved tracks, there may be intermediate pull-off masts which experience radial loads only, refer to Figure 1.



The spacing of the supporting structures is dependent on the geometry of the track. In straight track, the spacing is generally up to 73 metres. In 300 metre radius curved track the pull-off masts are spaced generally 30 metres apart.

Figure 1 : Fixed anchored system – partial long section showing intermediate pull-off masts



Figure 2 : Fixed anchor system - older-type support structure



3.2.2 Regulated systems

In a regulated system only one end of the wiring is fixed. The other end is an arrangement of weights and pulleys which apply a constant tension while taking up any slack in the wiring resulting from temperature variations. The tension in the system is said to be regulated. The height of the contact wire is thus maintained at all times and unaffected by temperature variation. Both the catenary and contact wires are regulated.

At support locations the OHW is supported by cantilevers which are supported from drop verticals or masts. The connection of the cantilever to the drop vertical or mast is a hinge which allows the cantilever to swing freely longitudinally. A typical support structure and moving anchor is illustrated in Figure 3.

The typical maximum ‗tension length‘ between the fixed end and moving end is approximately 1000 metres. For 1000 metre tension length OHW conductors move about ±500mm under the extremes of temperature (typically -5o C to 60o C). If the tension length were to be increased beyond this limit, the tension losses which accumulate at every support location would lead to inadequate system tension towards the fixed end, and will affect the contact stagger at temperature extremes.

Similar to fixed systems, the spacing of supporting structures is dependent on the geometry of the track. For straight track the maximum typical spacing is 67 metres, reducing to 28 metres for 200 m radius curved track.

3.3 Types of registration

There are two different systems in use for supporting and registering the wiring at each structure, these are:

Non-independent registration; Independent registration.

'Registration' refers to the precise lateral positioning of the contact wire (setting the stagger) to achieve the best interaction between contact wire and pantograph.

3.3.1 Non-independent registration

The wiring of multiple tracks is positioned over the tracks by means of a single catenary span wire and/or a single contact span wire, as illustrated in Figure 2.

3.3.2 Independent registration

The wiring of each track is supported independently of other tracks by means of a cantilever attached to a drop vertical or mast. Regulated systems are usually independently registered. Since 1985 all new or upgrade OHW has been independently registered which aims to improve reliability and minimise disruption to train services in the case of OHW failure.

3.4 Comparison of the systems

The major drawback associated with fixed anchor systems is the sagging of the wires with a rise and fall in temperature. Hence this type of system has problems around low vertical clearance structures such as overbridges and footbridges. During high temperature there is a risk of the sagging wire touching the roof of a train resulting in loss of power supply. Low temperature causes reduced clearances to structures spanning over the wire and increased tension in the wire resulting in higher loads.



Regulated systems provide good pantograph performance at speed and in high and low temperatures. They are RailCorp's preferred systems for new and upgraded wiring, although in some cases such as tunnel projects a fixed system may still be installed.



Figure 3 : Regulated system- single masts supporting the through-running wiring and functioning also as an anchor structure



The non-independent registration system has the disadvantage that a broken contact wire or span wire may result in a loss of correct contact wire position across multiple tracks affecting reliability.

The independent registration system has the advantage of losing only one track service in the event of a wiring incident. Much of the RailCorp network is now independently registered. All new and upgraded wiring is independently registered.

3.5 Wiring combinations

The following catenary and contact wire combinations are currently found in the RailCorp network:

Regulated Systems

Independent registration with twin catenary and twin contact wire; Independent registration with single catenary and either single or twin contact wire.

Fixed Anchored Systems

Single catenary with single or twin contact wires; Compound catenary system, in which there is a second (―compound‖) catenary

located between the main catenary and the contact wire, as used on the Main West beyond Penrith up to Lithgow.

Any of the above arrangements may have an 'auxiliary feeder', an extra cable running parallel to the main wiring, which is added to enhance current-carrying capacity.

In both regulated and fixed anchored systems a range of sizes (diametres) of catenary and contact wires are used, depending on the current-carrying capacity required in each particular section of the network.

3.6 Conversion from fixed anchored systems to regulated systems

As noted previously the type of overhead wiring system varies throughout the RailCorp electrified area.

Since about 1980 many lines have been upgraded from the original fixed anchored system, to a regulated, independently registered system with single or twin catenary and single or twin contact wires.

3.7 Overlaps

The maximum tension length in a regulated system is usually limited to 1000 metres. Continuity of the wiring between one tension length and the next is achieved by overlapping the wiring. As one set of wiring goes 'out of running' and terminates on an anchor structure, the next set of wiring comes in and goes 'in running'. This transition from one contact wire to the next takes place in an overlap usually of one 'bay length' (i.e. the distance between two structures).

When designing a regulated system, the electrical designer determines which end of the tension length is to be the moving end and which end the fixed.

In some cases, as determined by the electrical designer, two tension lengths (up to 1000m each) are created from a single run of wiring (i.e. up to 2000 m long), with moving anchors (and overlaps) at each end and a fixed mid-point (FMP - no overlap) in the middle.



4 Overhead wiring structures

Overhead wiring structures (OHWS) are provided to support the overhead wiring system, both fixed and regulated, with either independent or non-independent registration.

4.1 Structure types

The basic types of OHWS, for which there are standard drawings giving approved details, are as follows:

Single masts; Cantilever masts; Portal structures; Anchor structures (guyed); Anchor structures (free standing); Walkway structures (signal or feeder).

4.1.1 Single masts

Single masts are usually constructed from a universal column with a fixed base. The base fixity is provided either by a base plate and holding down bolts cast in a reinforced concrete footing (HP) or as a long length of steel potted in an augured hole with lightly reinforced concrete surround (PP). Standard steel sections are either 250UC73 or 310UC97.

In the case of two-track locations with independent registration, single masts are usually used in straight or slightly curved track locations to pull or push the wiring to the desired location over the track. However, single masts cannot be used in a pushing role on sharper curves, in which case portal structures with drop verticals are required. An example of a single mast can be found in Figure 4 (a).

4.1.2 Cantilever masts

Cantilever mast structures are made up of a vertical SHS mast and a horizontal boom with a drop vertical at its end. There are three standard sizes. They are commonly used in difficult locations to avoid the need for an excessively large or complex portal structure. Examples include: multiple-track locations with turnouts; two-track locations with (on one side of the tracks) a steep embankment or narrow access or signal sighting issue. Examples exist on the North Shore Line and on the Main West.

Cantilever masts are only used where neither single masts nor portals provide a good solution, because cantilever masts are prone to excessive deflection and are not as resilient as portals in the event of footing movement or accidental overloading of the structure. An example of a cantilever mast in use is shown in Figure 4 (b).

(a) typical single mast

(b) typical cantilever mast



Figure 4 : Typical use of single and cantilever masts

4.1.3 Portal structures

Portal structures consist of a ‗bridge‘ spanning between two masts. They are usually constructed with knee bracing and may have multiple spans. They provide independent registration of the wiring via drop verticals. There are several standard sizes ranging between 200SHS and 460 Double UB.

Examples of portal structures are provided in Figure 5 (a) and (b):

(a) in overlap, with twin drop verticals

(b) fixed system, independent registration

Figure 5 : Examples of portal structures

4.1.4 Anchor structures (guyed)

Guyed anchor structures can be any of the above basic structure types, guyed in the along-track direction at overhead wiring termination points. The guy rods are anchored to guy footings or guy anchor brackets (on walls, tunnels and other structures). A typical moving anchor with twin weight stacks on a single mast is shown in Figure 6 (a).

Where a moving-end anchor structure is proposed to carry twin weight stacks side-by-side there may be an infringement of track clearances, in which case two separate masts may be used, each carrying one weight stack, with guys used to tie the masts together and to the guy footing, as shown in Figure 6 (b).

(a) moving anchors, single masts, twin weight

stacks

(b) moving anchor, tied single masts with

separated weight stacks

Figure 6 : Typical guyed anchor masts



4.1.5 Anchor structures (free standing)

Free standing anchor masts (FSAMs) are not guyed and can be either a standard section or boxed. Standard steel section is 310UC. They are only used where site restrictions prevent the use of guy footings. They should be avoided if possible as they are not economical structures, they are prone to deflection and there is no structural redundancy.

Where a FSAM is required to carry twin weight stacks at a moving end, the boxed type FSAM must be used. The 310UC section of the boxed type is oriented at 90 degrees to the standard section (i.e. not boxed) type, to allow a weight stack to be mounted on each flange.

Examples of standard section and boxed free standing anchor masts are provided in Figure 7 (a), (b) and (c).

(a) FSAM – fixed

anchor

(b) FSAM, moving anchor, single weight

stack

(c) Boxed FSAM,

moving anchor, twin weight stack

Figure 7 : Examples of free standing anchor masts

4.1.6 Walkway structures

Walkway structures include signal gantries and some feeder structures. They are typically portals (or cantilever masts) of double channel or double UB construction with access ladder(s) and walkway and where required, signal cages.

Examples of walkway structures are shown in Figure 8 (a) and (b).



(a) signal gantry

(b) feeder structure

Figure 8 : Examples of walkway structures

4.2 Drop verticals

Drop verticals are short vertical members of 150 UC which are fastened to a portal bridge or boom of a cantilever mast. They are used to provide independent registration of the wiring.

There are two basic types of drop verticals in use, these are:

Single drop verticals (DS); These are usually located between tracks to provide independent registration for one or two adjacent tracks.

Twin drop verticals (DT); These consist of two single drop verticals one metre apart, welded into a single assembly. They are generally used in overlaps where there can be two sets of wiring above each track.

The height and offset of each drop vertical in relation to a specified track is nominated by the electrical designer. The civil design engineer must convert this data into a drop vertical length and a horizontal distance from face of mast. This information is to be presented on the Structure Diagram.

4.3 Footings

The loads to be carried by OHWS footings are mainly lateral forces and moments rather than vertical forces.

There are three standard types of OHWS footings;

Regular (box shaped excavated footing); Piled; Footing in Rock; These are typically used on top of rock cuttings. The strength

comes from reinforcing bars grouted into the rock. This configuration is not to be confused with a regular footing embedded or socketed into rock.

The choice of footing is usually determined by construction requirements or site conditions. A piled footing is generally the most economical option however site factors such as in-ground services or machine access issues often lead to the use of regular (excavated) footings. A standard note is normally used on the Structure Diagram drawing which allows for selection of footing type (regular or pile) by the construction engineer.

The footing in rock can only be used if specified on the Structure Diagram. This type of footing is for use on top of rock cuttings and not for footings at cess level, because the stability of these footings can be lost if there are any adjacent excavations (for new services or cess cleaning) or if the grouted bars corrode due to water at cess level.



Footings at cess level in rock cuttings usually have to be regular type, hammered out of the rock.

Examples of the three standard types of footings are provided in Figure 9.

(a) typical regular footing

(b) typical piled footing

(c) typical footing in rock

Figure 9 : Standard footing types

4.4 Attachment to other structures

Overhead wiring may sometimes be supported by structures other than overhead wiring structures, such as overbridges, footbridges, tunnels and airspace developments. In some cases there may be a suitable standard electrical fitting to support the wiring from these structures, otherwise an attachment detail, such as a special drop vertical or special anchor bracket, will need to be developed by the civil design engineer. The effect of the added load on the structural integrity of the supporting structure (especially in the case of anchor loads) must be considered.

Examples of attachments to other structures are shown in Figure 10 below.

(a) special drop vertical on tunnel roof

(b) special anchor brackets on abutment of overbridge

Figure 10 : Examples of attachments to other structures



4.5 Standard drawings

As noted in Engineering Standard ESC 330, a suite of standard drawings has been developed for the various overhead wiring structure types and structural components, for use within the RailCorp network. A list of the current standard drawings is provided in Appendix 1.

The standard drawings provide standard details for masts, portal structures, drop verticals, footings etc. Elements which are detailed and dimensioned on the standard drawing (e.g. connections, kneebraces, holding down bolts) are already approved for use with that standard structure type. The selection of an appropriate standard structure type for each structure is the design responsibility of the civil design engineer.

The use of standard drawings provides the following advantages:

consistency in structure types including appearance and size; cost efficiencies in design, fabrication and installation; simplicity through limiting the number of standard electrical fittings required.

Standard drawings are to be used in conjunction with a Structure Diagram prepared for each individual structure. Any elements of the structure which are only partially detailed or dimensioned on the standard drawing (e.g. lengths of main members, drop vertical lengths, anchor details, some footing depths) are the design responsibility of the civil design engineer and are to be shown on the Structure Diagram.

The civil design engineer is responsible for designing any additional structural details required which are not covered by standard drawings, and is also at liberty to develop non-standard details which are considered to be an improvement on the standard drawings. In the latter case the civil design engineer should state the justification for departing from the standard drawings.

In the case of footings, the standard drawings generally give footing depths in table form for a range of foundation conditions. The allowable loadings associated with these footing depths are given in Section 5.8. It is the responsibility of the civil design engineer to ensure these allowable footing loads are not exceeded.

5 Design of overhead wiring structures

5.1 Design responsibility

The civil design engineer is ultimately responsible for ensuring each overhead wiring structure meets all limit state requirements including strength, stability and serviceability.

Design and design verification are to be undertaken by design engineers who are competent professional civil/structural engineers with delegated engineering authority.

The division of responsibility for design of the various components of the overhead wiring system is as follows:

Electrical Designer:

Catenary and contact wires; Droppers (used to hang the contact wire from the catenary); Overhead wiring support and registration arrangements, such as cantilevers; Tension regulators, i.e. weight stacks used at moving anchors; Guy rods and anchor arrangements; Standard anchor plates (used to attach a catenary, contact wire &/or guy rod to a

structure);



Other electrical items attached to the support structures including pull-off arms, insulators, OHW switches, feeder cables etc;

Loading diagrams providing information such as system weight and tension, radial loads, weight and configuration of any feeder/switch cables and equipment;

Drop vertical position and height information;

Civil Design Engineer:

Overhead wiring structures (e.g. single masts, cantilever masts, portal structures and anchor masts);

Associated structural details such as drop verticals, guy footings, access ladders and walkways, access prevention devices;

Non-standard attachments to other structures such as overbridges, tunnels and airspace developments;

Non-standard fittings required by the electrical designer, such as special anchor plates;

Liaison between the electrical designer and the civil design engineer is necessary during all stages of the project to resolve specific design problems.

5.2 Design procedures

Design of overhead wiring projects involves a number of design disciplines and stakeholders who need to combine all their requirements to produce the desired project outcome. Both the civil and electrical design process are undertaken at the same time along with the stakeholder input and review. To better understand this sometimes complex arrangement the following section outline these processes and assign responsibilities for deliverables and the timings involved.

5.2.1 Project stakeholder

All overhead wiring projects from a single structure replacement to a complete rebuild has many stakeholders involved. To insure that all stakeholder requirements are incorporated into the project a design process has been developed that allows for interaction amongst stakeholder during the design process to produce a solution that is acceptable to all.

Major stakeholders include:

Electrical Asset and Maintenance Engineers who are responsible for the planning, upgrading, inspection and maintenance of the overhead wiring and electrical fittings;

Civil Asset and Maintenance Engineers who are responsible for the planning, upgrading, inspection and maintenance of structures and foundations that support the overhead wiring;

Project Manager who is responsible for delivering the completed project to the Asset Engineers;

Electrical Construction who undertake the procurement and construction of the electrical components in accordance with the electrical design documentation;

Civil Construction who undertake the procurement and construction of the structure and their foundations in accordance with the civil design documentation;

Signal Asset Engineer who is consulted on mast placement and related signal sighting issues;

Regional Surveyor who is responsible for the horizontal and vertical track alignments.

A number of other departments have an input into the project and may also be involved in the design process. These are:



Geotechnical Engineers; Surveyors; Track Designers.

5.2.2 Project design process

While the following design procedure is generally adopted for major overhead wiring upgrading projects many of the processes will still take place during smaller design jobs:

a) Survey Data: aerial mapping of the proposed section of track under investigation by the project is obtained from the RailCorp aerial mapping data base. The aerial mapping needs to be reviewed to determine if the quality and accuracy of the information is relevant for the project. If the information provided on the aerial mapping is insufficient, arrangements to supplement it with field survey or additional aerial mapping may need to be arranged. The aerial mapping and other electronic information obtained from the GIS section will allow a base plan to be developed which will identify existing boundaries, structures, platforms, buildings, bridges, etc. This base plan is developed by the electrical designer with inputs provided by the Design Delivery Manager;

b) Track alignments: for projects associated with existing tracks the design vertical and horizontal alignment are obtained from the Regional Surveyor and developed into a Microstation model by Track Design. If new track work is involved then the design vertical and horizontal alignments will be obtained from the track designers;

c) Preliminary overhead wiring layout plan: this layout plan is prepared by the electrical designer and is produced by combining the base plan with the horizontal track models and any existing overhead wiring layouts. New structure locations are plotted on the preliminary layout plan showing the type of overhead wiring structures, wire arrangement, and anchorage. It is during this stage of the design process that the civil design engineer may be involved by providing preliminary advice on suitable structure configuration and placement;

d) All-party walkthrough: this comprehensive stakeholder site inspection should include the project manager, civil and electrical designers, construction and local engineering maintenance staff. The purpose of the walk-through is to identify any site constraints, other proposed work in the area, services affected (electrical & signal cables, track drainage, water mains, etc.), signal sighting issues, and to ensure constructability of the footings. Depending on the outcome of the walk-through, adjustments may need to be made to the location of certain structures;

e) Survey: once the locations of the structures are confirmed, a survey cross section for each structure is requested. The survey field data is drawn up as a CAD cross section, with design track data added, and this becomes the basis for the civil Structure Diagram;

f) Electrical loading diagrams: the electrical designer prepares an Electrical Loading Diagram for each structure, showing the basic structure type (single mast, portal, etc) and the forces in kilonewtons due to the weight load, wind load & radial load of each wire supported by the structure. The Electrical Loading Diagram constitutes authorisation from the electrical designer to the civil designer engineer to proceed with design of the structures;



g) Civil design: the civil designer carries out the necessary structural analysis and other design calculations, using the results to determine an appropriate standard structure type and carries out design of any non-standard details. A Structure Diagram is prepared for each location showing as a minimum the following: structure number; standard structure type; footing(s) type; lengths of main members; drop vertical details if any; anchor details if any; non-standard details (or reference) if any; RLs for top of pedestal of footing(s); coordinates of mast centreline(s); track data; terrain. Refer to Section 8 for full documentation requirements.

5.2.3 Civil design process

The process described above deals with the project as a whole and notes at what point Civil Design input and output is required. This section expands on the civil design process giving greater detail on what steps are undertaken in the design of overhead wiring structures.

a) Provide civil design advice to the electrical designer during the development of the preliminary overhead wiring structure layout. Input at this stage of the design process is usually only required on projects or structure locations that are complex. A combined approach with Electrical Design produces a result that both parties are able to develop satisfactorily during the final design stage. An added benefit is that the civil design engineer gets an advanced understanding for the possible complexity of the project.

b) If the project is large or complex enough the civil design engineer will need to participate in the preliminary walkthrough with the electrical designer. During this stage the civil design engineer needs to provide input into structure locations and in particular where the mast will be located. Issues such as constructability, signal sighting and mast offset to avoid existing rail services are discussed and resolved. These issues should be noted down and agreement obtained during the all-party walkthrough.

c) The all-party walkthrough is an opportunity for the civil design engineer to gather valuable design input about each of the structures to be designed and relevant ground conditions. Photographs of the structure location and each footing location should be taken to help with recall of any particular requirements during the documentation stage. Civil Construction representatives should be consulted during the walkthrough about any issues they have that need to be addressed during the design. Often they will nominate what type of footing they would be likely to construct (piled or regular), along with placement to suit their work methods (day works or possession works). The Civil Asset Engineer may have some requirements that will affect the design and these should be recorded to ensure the design reflects these requirements.

d) Using the structure layout drawings and Electrical Loading Diagrams sort structures into similar types and configurations to produce groups of structures. Structures in a group should have similar parameters such as span lengths, drop vertical configuration, total weight load and radial load. Due to the wide range of parameters that commonly occur within a project, it is possible there may be many structure groups required and not many individual structures in each group. Select one structure from each group as the design structure to represent that group. The selected structure should be the heaviest loaded and the longest span or a combination worst case. The reason for grouping structures is to maximise efficiency of the design process, but this must not be at the expense of structural efficiency i.e. grossly conservative design which may result from lumping significantly



different structures together in one group is not acceptable. Past experience has shown that grossly oversized structures in the rail corridor encourage negative attitudes towards Railcorp from the public and from field staff. To ensure economical use of steel sections keep grouped structures within the range of suggested maximum span lengths nominated for each standard structure given in Table 1.

Standard Portal Type Suggested Maximum Span Length (m)

200 SHS 14 250 SHS 20 300 SHS 25 300 DC 27

Table 1 : Suggested standard structures maximum span lengths

e) For each chosen structure determine the appropriate standard size steelwork required by using proven designs or full structural analysis. If proven designs are used the design process will continue at (j). For proven designs to be a valid method the span length, configuration and loadings must be similar to another structure where full design calculations have been undertaken. Reference to this structure and calculations needs to be included in the design documentation.

f) Design loadings for all structural members of the chosen structure are determined. Electrical Loading Diagrams are used to obtain loadings produced by the attachment of the overhead wiring to the structure. Static loads, live loads and wind loading on the structure are determined using Australian Standard AS 1170 and RailCorp Standard ESC 330. Appropriate strength and serviceability load combinations for the structure are determined using Australian Standard AS 1170.0. A detailed explanation of these loadings and combinations is provided in Section 5.4 of this manual.

g) Once all the loadings have been determined the structure is modelled using industry structural analysis software. RailCorp use either Microstran or Strand to model overhead wiring structures. The structure span length is determined by summing track centres obtained from the design horizontal alignments, and mast offsets agreed to on the all-party walkthrough. Drop vertical locations, wire and anchor heights are obtained from the Electrical Loading Diagrams and structure layouts. Section properties are usually generated by the software for the specific sections nominated. Loadings determined in (f) are applied to create a structural model representative of the structure being designed. Analyse the structure for the determined load cases and check the output for any extraneous results. A detailed explanation of structural modelling techniques for overhead wiring structures is provided in Section 5.5 of this manual.

h) Using the results produced for the strength limit state load cases, check the steelwork section and member capacity for compliance with the requirements of Australian Standard AS 4100. This design activity can be undertaken by hand calculations but most analysis software has an attached design component that will check the sections modelled. The use of correct analysis type, restraint type and member releases are essential to obtain a correct result from the software. Section 5.6.1 of this manual provides guidance in these areas.

i) The steelwork sections selected for the structure are then checked for compliance with serviceability requirements in RailCorp Standard ESC 330. Serviceability requirements consist of lateral deflection at the contact wire



under wind loading and aesthetic appearance of the structure under static loading. Section 5.6.2 of this manual provides guidance on serviceability requirement application.

j) All standard overhead wiring structure steelwork drawings have associated standard footing drawings. The design engineer must confirm that the design loadings do not produce design reactions on the footings greater than the allowable loadings for which the footings have been designed. The preferred footing type is nominated at this stage for inclusion on the Structure Diagram. If the allowable loadings are exceeded then specific footing depths will need to be calculated and noted on the Structure Diagram. Overhead wiring structure footing design is addressed in Section 5.8.

k) A Structure Diagram is the design output generated by the civil design process. A Structure Diagram for each structure location is produced that provides information such as structure type and size, mast location and track offset, dimension required to fabricate standard steelwork, anchor drilling heights and notation, drop vertical type, length and position etc. Documentation requirements for Structure Diagrams and other design outputs are addressed in Section 8.

l) Preliminary Structure Diagrams and any special structure drawings are released for review and comment to Electrical Design and Stakeholders. When all review comments are addressed the Structure Diagrams are completed including design verification and drafting check.

m) All drawings are released for construction by lodging them in the RailCorp Plan Room where they become accessible to all who are involved in the Project. The RailCorp Plan Room is the central depository for all drawings and holds the current amendment.

5.2.4 Structure types - order of preference

Where options are available to the designer as to the structure type to be specified at a particular structure location, there is an order of preference to apply, as follows.

1st Preference: Single masts, PP type - usually the simplest and most economical solution;

2nd Preference: Single masts, HP type - more expensive than a PP mast in the costs of fabrication and footing construction, but often required where, for example, footings may be foul of underground services, or are founded in rock, or where there is limited overhead clearance for erection of the mast;

3rd Preference: SHS portal - a simple and reliable portal structure, it is typically used to span across multiple tracks or on curves in two-track locations if single masts cannot be used;

4th Preference: Cantilever mast - susceptible to excessive deflection if static loading is high or if ground is not stable, see below for further remarks;

5th Preference: DC or DUB portal - for long spans; fabrication costs are high;

With regard to cantilever masts, these may be specified in preference to SHS portals for a range of reasons, such as in the following examples:

to support a single track in multiple-track locations, such as a turnout in a yard, which would otherwise require a long span portal carrying only one set of wiring;

to avoid construction of a portal footing which may interfere with underground services or block an access road;

to avoid erection of a portal mast which is going to block sighting to a signal;



to enable improvements to cess drainage in a narrow cutting by omitting portal footings along one side.

It should be remembered that, all else being equal, the SHS portal is preferred over the cantilever mast.

For anchor structures, guyed anchor masts are always used where possible in preference to free standing anchor masts.

In general, site conditions, stakeholder requirements, and many other factors may cause preferred structure types to be ruled out at particular locations, and less-preferred types to be specified, in which case the designer shall make a record of the reasoning behind these decisions (in the form of a structure list or tabulation for example) and keep this document with the design calculations.

5.3 Design inputs

The design process for overhead wiring structures requires a number of design inputs from a range of different sources. It is essential that these inputs are obtained in a timely manner to ensure the design and documentation of the structures is undertaken as programmed.

Table 2 lists the major design inputs, responsible party for their generation and by what stage in the Civil Design process the input is required:

Design Inputs Generation Source Required Timing

Preliminary overhead wire structure layout plan.

Electrical Design. Before all-party walkthrough.

Civil construction requirements.

Civil Design from input provided by the civil construction representative.

During the all-party walkthrough with outstanding issues resolved before commencement of detail design.

Asset engineers requirements.

Civil Design from input provided by the Asset Engineer representative.

During the all-party walkthrough with outstanding issues resolved before commencement of detail design.

Final overhead wire structure layout plan as agreed by all participants on the all-party walkthrough & stakeholders.

Electrical Design. Before commencement of detail design and documentation.

Loading diagrams. Electrical Design. Before commencement of detail design and documentation.

Survey cross sections for each location in Microstation V8 format. Must also show design track centres, rail heights and super based on the design alignments.

Survey for field work and Track Design for generation of electronic cross sections.

Before commencement of detail design and documentation.

Drop vertical position and height table.

Electrical Design. Before half way through the detail design. An agreed date to be



determined. Geotechnical investigation and design parameters, if required (see below).

Geotechnical Services. Before half way through the detail design. An agreed date to be determined.

Services searches. Design Delivery Manager.

As agreed with DDM.

Table 2 : Design inputs

Geotechnical investigation may not be required at the design stage for some OHWS projects as the footing design is based on the use of standard drawings. For locations where the standard footings are not suitable, due to a highly loaded structure or some construction or site constraint that leads to a special structure or footing being required, then a geotechnical investigation will be requested during the all-party walkthrough. Geotechnical input will be required during the construction phase of the project to confirm the foundation material and subsequent footing depth as nominated on the standard drawing.

5.4 Loadings

To design an overhead wiring structure that is both economical in structure size and compliant with both strength and serviceability limit state requirements of the steel structures code and RailCorp standards, it is essential that all loadings that affect the structure are understood and applied. This section of the manual examines loadings that an overhead wiring structure will experience, how they are derived and how they should be grouped when designing.

Overhead wiring structure loadings are derived from two different sources. These are:

Overhead wiring, fittings and anchors that are attached to the structure. These loadings are supplied by the electrical designer in the form of an Electrical Loading Diagram.

The second source of loading is determined by the civil design engineer and must account for the weight and geometry of the structure, live and construction loadings, and the effects of wind on the structure and wire.

5.4.1 Electrical loading diagrams

Electrical Loading Diagrams are produced for each structure and contain a large amount of information that must be interpreted by the civil design engineer and combined with structural loadings to provide a complete structure loading.

Both graphical and tabulated information appear on the Electrical Loading Diagram and must be read in conjunction to obtain the loading information required to transfer to the structural design model. The graphical information on the loading diagram provides the designer with a structure configuration showing mast locations in relation to track and, for portals, the location and configuration of drop verticals. Each attachment of the wiring to the structure is numbered for reference to a column in the tabulated section of the loading diagram. Loading relevant to the numbered attachment points are provided in the table giving weight loads, radial loads, wire wind loads and anchor loads. Heights above rail level for each loading is given, with the datum track being the track that the wiring is servicing or, for anchors, a nominated reference track.

Figure 11 is a typical Electrical Loading Diagram with the major load types highlighted.



Figure 11 : Typical electrical loading diagram



5.4.2 Primary load cases

All loading types associated with overhead wiring structures have been assigned to a particular primary load case. The primary load cases that have been determined for design are based on grouping similar actions such as permanent effect, transient effects and wind loading together that allows application of suitable load factors to each but still producing enough flexibility in load cases to produce combinations that will produce the desired strength and serviceability results. Adopting a consistent primary load case configuration for the design of all overhead wiring structures will allow inputs and results from different designs to be easily understood and compared. The design verification and review process will also be enhanced. Primary load cases used in the design of overhead wiring structures are:

LC1 - Weight Load; LC2 - Live Load; LC3 - Radial Load; LC4 - Wind Wire X; LC5 - Wind Structure X; LC6 - Wind Structure 45; LC7 - Wind Structure Z.

5.4.2.1 LC1 - Weight Load (WL)

Loadings in this load case consist of all elements of the overhead wiring structure and wiring system that are static and produce a loading through the effects of gravity. These are:

Self weight of structural elements: Masts, bridge, kneebrace and drop vertical used in the modelling of the structure all add weight. When using engineering software if correct member sizes are specified this loading is generated by applying a gravitational load to the load case.

Static weight load of wiring system: The overhead wiring, which consists of catenary and contact wire and an in-span dropper system that connects them together, has a weight component that is transferred to the structure at the registration point. Each overhead wiring configuration has a different system weight per metre length due to the different combination of contact and catenary configurations and wire sizes. The Electrical Loading Diagram provides the static weight load at each attachment point which is added to the structural model in Load Case 1. Figure 12 is a portion of a typical Electrical Loading Diagram showing static weight loading for registration points.

Figure 12 : Typical static weight loading

Static weight load for terminating wires is also obtained from the Electrical Loading Diagram. Refer to Equipment Number 4 column in figure 11. The loading is applied to the catenary anchor plate when both contact and catenary anchor plates are used.

Self weight of electrical fittings: The electrical fittings used to support and register the wiring form part of the weight load that the structure experiences. This loading, although produced by electrical components, is not included in the static weight



load on the Electrical Loading Diagram. An allowance for different regulated electrical fittings shown in Figure 13 (a) and (b) needs to be added to the load case where applicable. This loading is considered to act at a point halfway between the track centreline and the mast or drop vertical.

(a) typical mast registration equipment

(c) typical termination equipment

(b) typical drop vertical registration equipment

Figure 13 : typical self weight of electrical fittings

The design engineer needs to add a weight allowance for moving anchor terminations as shown in Figure 13 (c). A value of 1.0 kN is applied at the anchor plate and 0.4 kN to the mast for each weight stack. The application of these loads to the structural model is described in Section 5.5.2.1.

Self weight of anchor stack weights: This loading is only applicable if a moving end of the overhead wiring run is anchored to the structure. The weight stack that provides tension to the overhead wiring is attached to the mast at the anchor plate and loads the structure mast with an axial load and moment. The loading depends on the tension required by the overhead wiring which is shown on the Electrical Loading Diagram. To calculate the vertical weight load the regulated tension value is divided by three (3) as the tensioning system uses pulleys to provide a 3 to 1 mechanical advantage. The total vertical force that the tensioning weights provide at a termination point is given in the Electrical Loading Diagram. Refer to Total Weight Stack value given in Equipment Number 4 column in Figure 11.

5.4.2.2 LC2 – Live Load (LL)

Overhead wiring structures are non trafficable and therefore not subject to any design live loading being applied directly to the structure but must be designed to accommodate a construction loading as defined by Electrical Design of 1.07 kN per track attached to the structure. This loading is to represent a person standing on the contact wire during construction and maintenance activities. The loading is transferred to the structure via the wiring registration points. (Note, the ‗dynamic weight load‘ seen under the static weight load in the current loading diagram was formerly used to represent live load but should no longer be used in structural design.)



5.4.2.3 LC3 – Radial Load and Anchor Load (RL)

Radial and anchor loading on an overhead wiring structure is produced by geometrical and tension effects caused by the overhead wiring where it is attached to the structure. These are:

Catenary and contact radial loads: The catenary and the contact wire are tensioned and where they attach to each structure the wires change direction. It is the change in direction that produces the radial loading on the structure. The value of the radial load is dependent of the amount of directional change and tension in the wire. Radial loads are provided by the electrical designer as they design the wiring and its geometry. The Electrical Loading Diagram provides both catenary and contact radial loads for all attachment points. These values and the heights at which they apply are used to generate Load Case 3 inputs.

Figure 14 is a portion of an Electrical Loading Diagram with highlighted examples of catenary and contact radial loads and the height above the track that they service.

Figure 14 : Examples of typical catenary and contact radial loads

Anchor termination loads: A source of loading that needs to be considered for some structures are the components generated by wire terminations. In plan view, the anchor wire is not attached exactly perpendicular to the structure, as the wire has come from above the track at the preceeding structure. Therefore this load splits into two components, a large longitudinal load and a smaller lateral load. The Electrical Loading Diagram provides the anchor tension, anchor attachment angle, the lateral component generated and the height above the reference track. Refer to Figure 11, Equipment Number 4, for an example of anchor termination loads. The longitudinal component may be calculated by the civil design engineer using cos (anchor attachment angle) x (anchor tension), but may be taken conservatively as equal to the anchor tension. Anchor attachment angle is relative to the perpendicular (plan view).

Fixed mid-point loads: Another source of loading that must be applied at a few locations is the out of balance loading that is found at fixed mid-point portal structures. At approximately half way between the moving ends of a two-tension-length wire run the catenary is attached to the underside of a portal bridge using a post type insulator. The contact wire is anchored at the same location by bridle



wires that tie back to the catenary wire on either side of the anchor point. Figure 15 (a) and (b) show a typical fixed mid-point arrangement for a portal structure.

The wire run now has a moving anchor at each end of the run with movement restricted at the fixed mid-point. The tension lengths either side of the fixed mid-point will vary in length as will the number of supporting structures and the amount of directional change experienced by the wires. Equal tension is applied at the moving ends of the run but each half undergoes different amounts of differential losses which results in different tensions at the fixed mid-point.

(a) sectional elevation at a fixed mid-point structure

(b) longitudinal elevation at a fixed mid-point structure

Figure 15 : Typical portal fixed mid-point structure

Tension differential in the wire is transferred to the structure via the post type insulator. The electrical designer nominates fixed mid-points on layouts and Electrical Loading Diagrams. A maximum out of balance loading of 2 kN per wire run attached to the structure is usually specified. The loading could occur in either out-of-plane direction and should be applied in the direction to produce the worst effect when in combination with other radial loads and the effects of wind.

Figure 16 : typical single mast structure fixed mid-point



A fixed mid-point structure must also be checked for compliance with strength limit state under an extreme load event. If the catenary and contact wires for one track break then the full system tension for that track could be transferred to the portal bridge. The clamps locking the catenary wire at the portal should slip at around 5 to 7 kN load but in the event they do not (such as if the wire jams) the structure will experience a large out-of-plane load. The load should be considered in conjunction with other weight and radial loads but not live load or wind loading. No load factor should be applied and deflection compliance is not required. It is customary to guy the masts of a fixed mid-point portal (both sides of each mast) to guard against the risk of structural collapse under an extreme load event.

A fixed mid-point can also be used when the wiring for a track is supported by single mast structures rather than portals. The fixed mid-point is formed over two bays by running an anchor wire between masts placed on the same or opposite sides of the track. The anchor wire crosses the catenary wire at the mid-point structure, where the wires are clamped together and the catenary tensioned. Bridle wires are placed either side of this point to secure the contact wire. Structures at both ends are designed as fixed anchor structures with the loadings provided by the electrical designer. Consideration also needs to be given to the anchor structures for the extreme load event as per the fixed mid-point portal structure. Refer to Figure1.6 for a typical single mast structure fixed mid-point elevation and plan.

5.4.2.4 LC4 – Wind Wire X (WWX)

The overhead wiring is exposed to the elements and experiences a loading that is generated by the wind. Overhead wiring bay lengths can span up to 70 m and the wind loading developed over this length is transferred to the attachment point at the structures. Wind loads can become significant especially when twin catenary and contact wiring are used.

Traditionally the electrical designer has provided wind loadings as part of the Electrical Loading Diagram. These loadings were developed when the civil design for overhead wiring structure was undertaken using working stress methods. As the structures are now designed using limit state methods the wind loading that is applied needs to be calculated using ultimate regional wind speeds and serviceability regional wind speeds corresponding with the wind loadings applied to the structure. (The ‗dynamic wind load‘ given for each wire in the current loading diagram should no longer be used.)

Wire wind loading is determined in accordance AS/NZS 1170.0 and AS/NZS 1170.2. The ultimate regional wind speed is determined from Table 3.1 in AS/NZS 1170.2:2002 with importance level and design working life obtained from Table 3 of this manual and annual probability of exceedance from Table F2 in AS/NZS 1170.0:2002. Serviceability regional wind speed is determined using average recurrence interval of 25 years.

Overhead Wiring Structure Condition Usage

Importance Level

Design Working Life (Years)

New structures supporting overhead wiring over tracks carrying passengers 2 100

New structures supporting overhead wiring over tracks not carrying passengers (e.g. stabling sidings)

1 100

Existing structures (25 years or older) supporting overhead wiring over tracks carrying passengers

2 25

Existing structures (25 years or older) supporting overhead wiring over tracks not carrying passengers (e.g. stabling sidings)

1 25



Table 3 : Importance level and design working life

To remove the need to calculate the wind loading from first principles each time a structure is designed a number of tables have been generated so the loading for the particular wind span and wire configuration is simply determined. The tables have been calculated using code requirements and principles on the conservative side of design values. Theory behind the development of the tables is presented in Appendix C along with a large copy of each for use in design. The calculations should be viewed by all designers to appreciate the origin of the values being used.

Catenary and contact wind loadings are determined from the tables using the following steps:

Determine topographical type: Loading tables for two topographical options are available. The majority of structures will be designed using the Normal option table as the Exposed option is for structure situated on embankments 10 metres or greater in height.

Determine the wind span: The wind span is the length of overhead wiring supported by the structure that is affected by wind loading. Wind span values are provided by the electrical designer as part of the Electrical Loading Diagram. A portion of an Electrical Loading Diagram showing wind span values is contained in Figure 17.

Determine catenary and contact wire configuration: Configuration of the catenary and contact wire is provided on the Electrical Loading Diagram. The values shown are the cross sectional area of the wire in millimeters squared. Some configurations have a (2x) placed in front of the cross sectional area to indicate twin wires. A portion of an Electrical Loading Diagram showing catenary and contact wire configuration is contained in Figure 17.

Figure 17 : Wind span, catenary and contact configuration example

Read wind load values from table: Using the loading table selected based on topographical option, as shown in Figure 18, find the wind span and read off catenary and contact wind load in the columns for the wire configurations in use.



Figure 18 : Example loading results for 48m wind span

The wind load on the wiring is determined for each attachment point on the structure under consideration. The loading is for wind perpendicular to the track, therefore in plane with the structure, and is applied in the direction (to down side or up side) that has the greatest effect on the structure when loaded in conjunction with other primary loadings.

5.4.2.5 Wind loading on structure

The overhead wiring structure is subjected to wind loading as it is an exposed structure with significant surface areas. The masts, bridges and drop verticals all need to have wind loading determined and applied. Three major wind orientations need to be investigated to determine the worst effects on the structure when in combination with other loadings. These orientations are:

LC5 – Wind Structure X (WSX): wind loading on the structure at 90 degrees to the track;

LC6 – Wind Structure 45 (WS45): wind loading on the structure at 45 degrees to the track;

LC7 – Wind Structure Z (WSZ): wind loading on the structure at 0 degrees to the track;

Structure wind loading is determined in accordance AS/NZS 1170.0 and AS/NZS 1170.2. The ultimate regional wind speed is determined from Table 3.1 in AS/NZS 1170.2:2002 with importance level and design working life obtained from Table 3 in Section 5-4.2.4 and annual probability of exceedance from Table F2 in AS/NZS 1170.0:2002. Serviceability regional wind speed is determined using average recurrence interval of 25 years.

To remove the need to calculate the wind loading from first principles each time a structure is designed a number of tables have been generated so the loading for the particular structural element under consideration is simply determined for the three wind directions. Theory behind the development of the tables is presented in Appendix D along with a large copy of each for use in design. The calculations should be viewed by all designers to appreciate the origin of the values being used.

For non-standard structural members where tables of wind loads have not been generated the designer must calculate wind loads from first principles and codes in the usual way.



Structure wind loadings for load cases LC 5, LC 6 and LC 7 are determined using the following steps:

Determine topographical type: Wind loading tables for two topographical options are available. The majority of structures will be designed using the Normal option table as the Exposed option is for structure situated on embankments 10 metres or greater in height.

Determine wind loading values for LC 5 – Wind Structure X: Using the output portion from the chosen topographical type table determine wind loading values (kN/m) for drop verticals, masts and bridge sizes from the IN PLANE column. An example output portion showing wind loading values obtained for a 300 SHS Portal is shown below in Figure 19. Note, the value obtained for the bridge is a frictional drag per metre.

Figure 19 : Example of 300 SHS portal in plane wind loads

Determine wind loading values for LC 6 – Wind Structure 45: Using the output portion from the chosen topographical type table determine wind loading values (kN/m), for drop verticals, masts and bridge sizes from the 45 DEG columns. An example output portion showing wind loading values obtained for a 300 SHS portal is shown below in Figure 20. Note, the value obtained for the x component of the bridge is a frictional drag per metre.

Figure 20 : Example of 300 SHS portal 45 deg wind loads

Determine wind loading values for LC7 – Wind Structure Z: Using the output portion from the chosen topographical type table determine wind loading values (kN/m), for drop verticals, masts and bridge sizes from the OUT OF PLANE column. An example output



portion showing wind loading values obtained for a 300 SHS Portal is shown below in Figure 21.

Figure 21 : Example of 305 SHS Portal out of plane wind loads

5.4.3 Combination load cases

Combinations of the primary load cases are used to determine limit state design loadings. These combinations have been developed from loading combinations specified is AS/NZS 1170.0. Combinations for each of the limit states that need to be considered by the design engineer are presented. It is the design engineer‘s responsibility to ensure all loadings applied to the structure have been captured in a primary load case and that the combination used is appropriate.

Limit state load cases used in the design of overhead wiring structures are:

Strength load cases; Serviceability load cases; Stability load cases

5.4.3.1 Strength load cases

Strength related design values are to be obtained from the load combinations shown below:

LC8 WL + RL 1.35*LC1 + 1.35*LC3 LC9 WL + RL + LL 1.2*LC1 + 1.2*LC3 + 1.5*LC2 LC10 WL + RL + WWX + WSX 1.2*LC1 + 1.2*LC3 + LC4 + LC5 LC11 WL + RL + WW45 + WS45 1.2*LC1 + 1.2*LC3 + 0.5*LC4+ LC6 LC12 WL + RL + WSZ 1.2*LC1 + 1.2*LC3 + LC7

Live load for OHWS is a construction loading which has a negligible probability of occurring in conjunction with an ultimate wind event. Therefore no combinations of live load and wind loading are used.

In load case LC11 the wind loading on the wire at 45o, denoted WW45, has been included by multiplying the WWX load by a factor of 0.5. This factor has been obtained from recommendations in AS/NZS 1170.2 Clause E2.1 (b) as the wire is a round cylindrical shape treated as a member inclined at 45o to the wind direction. Therefore Ki = 0.5.



Additional load cases for the strength limit state categories may be required when it is not possible by visual inspection to determine which direction the wind loading should be applied to produce the worst effect or when special loadings are specified.

5.4.3.2 Serviceability load cases

Two serviceability requirements are required to be fulfilled in order for an overhead wiring structure to be deemed to comply. Serviceability deflection values are to be obtained from the load combinations shown below:

LC13 STATIC DEFLECTION LC1 + LC3 LC14 CONTACT WIRE DEFL 0.65*LC4 + 0.65*LC5

Load case thirteen (13) is used to capture the deflection in the structure caused by static loading. Static loading is important as this produces the deflected shape which is normally visible to field staff and the public. If the static deflection is limited then the aesthetic appearance of the structure will be kept to what is visually acceptable. Large static deflections can lead to field staff raising concerns repeatedly throughout the life of a particular structure, or can lead to future remedial work being carried out which is unnecessary from a structural point of view.

Load case fourteen (14) captures the lateral deflection of the structure during serviceability wind loading in plane. The lateral movement of the contact wire needs to be limited to ensure pantograph security. The civil component is restricted to 50 mm by Electrical Design. A serviceability wind loading is determined by multiplying the ultimate wind load by a factor obtained by dividing the ultimate wind pressure by the serviceability wind pressure. A value of 0.65 is derived for structures with a design working life of 100 years and an importance level 2. Design of structures with different design working life and importance level will require recalculation of this value.

Three additional load cases are required so the footing reactions can be compared with the standard footing capacities. The allowable footings loadings were determined a number of years ago and are therefore working loads. Reactions for the structure need to be obtained in the serviceability format for comparison. Three serviceability load cases given below are generated for this purpose:

LC15 WORKING WIND X LC1 + LC3 + 0.65*LC4 + 0.65*LC5 LC16 WORKING WIND 45 LC1 + LC3 + 0.33*LC4 + 0.65*LC6 LC17 WORKING WIND Z LC1 + LC3 + 0.65*LC7

Load case sixteen (16) uses a factor of 0.33 to multiply the wind on the wire loading (LC4). This reduction factor is obtained by multiplying 0.5, which is used to reduce the wind load on the wire to obtain loading due to the 45o angle of the wire, by 0.65 to convert the ultimate wind load to a serviceability wind load.

The design engineer should note that the 0.65 is derived for a specific design working life and importance level. If these parameters change such as when analyzing an existing structure a new multiplier will need to be calculated.

5.4.3.3 Stability load cases

Stability of a new structure is taken into consideration in the determination of the footing depth. Stability needs to be examined when an existing portal structure with shallow footings is being analyzed. An existing portal, while stable in the in-plane direction due to frame action, needs to be checked for stability failure in overturning in the out of plane direction due to longitudinal wire movement and wind.

LC18 OUT OF PLANE STABILITY



0.9*[LC1(Fy) + Weight of Footing] > 1.2*LC1(Fz & Mx) + LC7

Using reactions obtained from the load cases and their components given in the above expression a stability calculation on the existing footing is undertaken. Using the pivot point of the existing footing and lever arms, calculated from its geometry, stabilizing and destabilizing moments are calculated.

For the existing footing to be considered to meet the stability requirements of AS/NZS 1170.0 the factored stabilizing moments must be greater than the factored destabilizing effects.

5.5 Structural modelling

The analysis of overhead wiring structures is usually undertaken using a commercially available structural analysis package. A number of different analysis packages, such as Microstran, Space Gass and Strand are available for modelling purposes. Regardless what package is used there are some modelling techniques and loading application methods that have been developed over time by RailCorp that should be adopted to produce a model that is a true representation of the structure.

Many of the Figures used in this section have been produced using Microstran but the ideas they convey are applicable to any analysis package. In the text and Figures used to describe the structural modelling the following global axes have been adopted:

X is horizontal, in plane i.e.perpendicular to the track; Y is vertical; Z is horizontal, out of plane i.e.parallel to the track.

If the structure is not complex hand calculations are sometimes used but many of the load application methods will still apply.

5.5.1 Modelling techniques

There are modelling techniques that can be applied at the structure input stage of the analysis that will enhance the models ability to be a true representation of the structure and extract results more efficiently. Using these techniques will help produce a model that provides an economical and efficient structure size.

5.5.1.1 Node placement

In addition to placing nodes in the usual modelling locations e.g. at the ends of elements and the intersection of members, it is very useful to place nodes at the following locations:

At contact wire height on a mast that has a registration point as this allows the location to be directly loaded with radial and wind loadings as well as having a nodal location to enquire on when determining deflection results.

At contact wire height on a drop vertical to allow radial and wind loading to be applied and to enquire on when determining deflection results. The drop vertical below the contact wire attachment location is not usually modelled as it only adds unnecessary complexity to the model.

At anchor attachment locations on a mast to allow all the loading associated with an anchor point to be modelled. Most anchor attachment points have guy rods connecting and the placement of a node allows this to be modelled so the resultant vertical force generated by the change in direction of the anchor wire is included automatically into the structure.



At splice locations in the bridge as this allows the forces at the splice to be determined easily so the splice capacity can be checked and the splice located in a position of minimal bending moment where possible.

The number of nodes placed in a structural model should be kept to a minimum. Placing unnecessary nodes produces additional result output that will have to be sorted through to find important result locations.

5.5.1.2 Member releases

The correct application of member releases allows the structure to distribute loadings between members as it would under real conditions. Close attention needs to be given to the connection details shown on the standard drawings to ensure the correct fixity is being applied to the structural model.

Some areas that require attention are:

Kneebrace connection at the mast and bridge for most of the standard structures consists of only four bolts in a closely spaced group attaching to the near flange. Transfer of full moment through this type of connection would not occur and it should have moment releases applied to each end of the member in the Z direction when modelling.

Connections to guy rod at the mast and guy block are pinned and transfer zero moment. When modelling these members a moment release in the members Z direction needs to be applied.

When modelling older type structures the connection between the mast and bridge will need to be assessed to determine if it can transfer moment as many of these connections were only simple angle cleats. Current SHS and DCP portals have moment connection at this location.

5.5.1.3 Section properties

Most steel components in an overhead wiring structure are standard hot rolled or cold formed section and are therefore easily modelled as the sectional properties are generated from the software library. A number of components are builtup sections that require the section properties to be determined by the design engineer undertaking the modelling.

Microstran has a function that allows sections to be generated using different configurations and orientations of standard sections to produce a new section. This section is then converted into a library section which can be used in the analysis and design components of the software.

RailCorp have developed a Microstran library containing builtup sections that are used on most of the standard structures currently in use. The library is named ‗Ohws.lib‘ and contains components found in Table 4.

When using these sections in a model the design engineer needs to be aware of a number of limitations that can be associated with their use. When the software calculates the torsional constant (J) used in the sectional properties it does so by simply adding the torsional property of the two sections nominated that make up the new member. This approach is correct for members such as the kneebraces as they are not heavily battened. For the bridge and mast sections of the DCP the calculated torsional constant is not a true representation as these members have diaphragms and close spaced battens that increase the torsional stiffness significantly.

Structure Component Section Category Section Name



200 SHS Portal

Kneebrace Dbl. Angles long legs

DALUC/SHS_K

250 SHS Portal 300 SHS Portal 250 SHS Cantilever Mast 300 SHS Cantilever Mast 300 SHS Light Cantilever Mast 250 SHS Double Cantilever Mast

300 Double Channel Portal

Mast Channels toe to toe CTT300_M Bridge Channels back to

back CBB300_B

Kneebrace Dbl. Angles long legs

DAL300x90_K

300 Double Channel Signal or Feeder Structure

Mast Channels toe to toe CTT300_SM Bridge Channels back to

back CBB300_SB

Kneebrace Channels back to back

CBB300_SK

380 Double Channel Portal

Mast Channels toe to toe CTT380_M Bridge Channels back to

back CBB380_B


CBB380_K

Cantilever Signal Structure

Mast Channels toe to toe Not Developed

Bridge Channels back to back

Not Developed


Not Developed

Table 4 : OHWS library section names

When using the inbuilt design package that many analysis packages have the design engineer needs to determine if the builtup section will behave as intended. Local buckling of the individual members that make up the new library section is not usually considered in the design rules associated with design packages. The design engineer needs to satisfy themself that the positions and number of battens is sufficient to allow the built section to develop section or member capacity before local buckling of the individual members in the builtup section occurs. This is especially relevant to kneebrace sections as the members only have one or sometimes two battens within their length.

5.5.2 Application of loadings

Each of the primary load case loadings needs to be applied to the structural model. The application method is dependent on the type of wiring system being used. As most new structures are required to support regulated systems the application of loadings to the structural model provided in this section will concentrate on regulated wiring. To simplify the structural model electrical cantilevers are not modelled, instead vertical loads and moments are used to simulate the loading effects they create.

5.5.2.1 Weight load application (LC1)

If all structural elements have been modelled correctly then applying self weight to the model is as simple as applying a gravitational load. In Microstran set the current load case to Load Case 1 and apply self weight by using the Loads tab on the top menu bar and move the highlighter to GRAV Load… and select. The dialog box shown in Figure 22



will appear and ―Apply G‖ is selected which will set the Y acceleration to -9.81 thus applying self weight to all modelled members.

Figure 22 : Applying self weight to structure

(a) typical drop vertical configuration

(b) typical drop vertical microstran model

(c) typical mast configuration

(d) typical mast microstran model

Figure 23 : Weight load and live load modelling

The electrical fitting weight allowance (W1) and the static weight load of the wiring system (W2) are added together and applied to the drop vertical or mast as a point load. A moment (Mz) to simulate this loading being applied via the electrical cantilever is calculated by adding the static weight load (W2) multiplied by the distance the drop vertical or mast is located from the track centreline, to the electrical fitting weight allowance (W1) multiplied by half the distance. For simplicity the vertical load and



moment are applied to the drop vertical or mast midway between the bridge and the contact wire height.

A second moment (Mx), in the out of plane direction, is also calculated to apply the loading generated by the swing of the electrical cantilever. The movement of the wire along the track can range from -500 mm to +500 mm. All new structures are designed to withstand this range of movement so the out of plane moment is calculated by adding the static weight load (W2) multiplied by a distance of 0.5m, to the electrical fitting weight (W1) multiplied by a distance of 0.25 m. The calculated moment is applied at the same location as the vertical load and in plane moment and needs to be applied in the direction that produces the worst effect when combined with wind in the out of plane direction. Figure 23 shows drop vertical and mast configuration and how the loading is transferred as a member load in the Microstran model.

Structures that are used as termination points for wire runs will have other weight loading that needs to be applied to the structural model. Both fixed and moving ends are attached to the structure via an anchor plate. The anchor plate is bolted to the flange and sometimes the web of the mast giving a moment connection which allows the anchor plate to extend beyond the mast‘s centreline to provide clearance for electrical fittings and weight stacks. The static weight load, self weight of anchor stack weights (moving ends only) and electrical fitting allowance are all transferred to the structure eccentric to the mast centreline.

Mast type Anchor

Type

Anchor Plate

EDMS No.

Anchor Plate

Fitting No.

Offset Dimension (mm)

In Plane Out of Plane

200/250/310UC Fixed EL 0009428 358/61 115/137/164 190 Moving EL 0009443 358/63 175/197/224 205 Moving EL 0016592 601/7 0 65

300x90 DCP Fixed EL 0009428 358/73 160 290 Moving EL 0009443 358/75 220 305 Moving EL 0016592 601/7 0 285

300x90 (Signal/Feeder)/380x100 DCP

Fixed EL 0009428 358/74 160/200 382 Moving EL 0009443 358/76 220/260 397 Moving EL 0016592 601/7 0 378

410/460 DUB Fixed EL 0009428 358/78 215/240 483 Moving EL 0009443 358/77 275/300 498 Moving EL 0016592 601/7 0 385

310UC118 / 310UC137 / 310UC 158 FSAM

Moving EL 0046204 601/58 0 220/225/230

Fixed EL 0366933 358/79 0 245/250/255

Table 5 : Anchor plate offset dimensions

In and out of plane moments are generated due to this eccentricity and are calculated by multiplying the combined weight load by the distances of the connection point on the anchor plate from the centre of the mast. The size of a moving and fixed anchor plate varies for different structure types and anchor configurations. The suggested distance to be used when determining the in and out of plane moments to be applied to the model are provided in Table 5.

If a mast type not listed in Table 5 is required the design engineer must calculate values relevant for the section size used and the anchor fitting nominated. Figure 25 shows sections at the anchor plate indicating how the offset dimensions are derived.



5.5.2.2 Live load application (LC2)

Construction live load can be located anywhere on the wire within the weight span but it is transferred back to the structure by the electrical cantilever. As with weight load the construction live load is applied to the structural model as a member loading through the drop vertical or mast. A vertical load (LL) and moment (Mz) are applied to simulate the electrical cantilever which for simplicity is not modelled. A vertical load of 1.07 kN at each attachment point is used. This load is multiplied by the distance from the centre of the track to the mast or drop vertical to determine the in plane moment. These loadings are applied to the member midway between the bridge and the contact wire height.

A second moment (Mx) is also calculated to apply the loading generated by the swing of the electrical cantilever. The out of plane moment is calculated by multiplying the 1.07kN construction load by a distance of 0.5 m. The calculated moment is applied at the same location as the vertical load and in plane moment. Figure 23 shows drop vertical and mast configuration and how the live loading is transferred as a member load in the Microstran model. No construction loading is applied to an anchor wire attachment as the system depth would be insufficient for a construction worker to stand and maintain stability.

5.5.2.3 Radial load and anchor load application (LC3)

Contact radial loads are simply applied to the drop vertical or mast at the node that has been modelled at contact wire height. Catenary radial loads are also applied to the drop vertical or mast but they are member loads located at catenary height plus 300 mm. The additional height allows for the depth of the insulators and attachments.

Radial loads always remain horizontal in the direction indicated on the electrical loading diagram. Care needs to be taken with electrical arrangements that ‗push‘ the wire to ensure the radial loads are applied to the model in the correct direction. Figure 24 shows drop vertical and mast configuration and how the radial loading is transferred as nodal and member loads in the Microstran model.







Figure 24 : Contact and catenary radial load modelling

Anchor termination loads are applied to the mast of the structure at nodes that have been modelled at the anchor attachment heights given on the Electrical Loading Diagram. Two components are used to represent the tension in the termination wire as it connects to the structure at an angle (in plan view) created by the wire coming from above the track at the previous structure. Most anchor attachment points are not at the centre of the mast but to an anchor plate that is offset in both the X and Z directions.

My=[(Fz1*X1)+(Fx1*Z1)]+[(Fz2*X2)+(Fx2*Z2)] (a) Anchor plate dwg numbers EL0009428 & EL0009443

My=(Fz1*X1)+(Fx1*Z1) (b) Anchor plate dwg number EL0016592

My=(Fz1*X1)+(Fx1*Z1) (c) Anchor plate dwg numbers EL0046204 & EL0366933

Figure 25 : Anchor termination load modelling

In addition to the component horizontal loads a resultant moment (My) is calculated using the equations given in Figure 25 and dimension of anchor plate offsets given in Table 5 and applied to each anchor node.

For fixed mid-points on portals the 2 kN out of balance load is applied to the bridge as a member load directly above the centreline of the tracks nominated by the Electrical Loading Diagram. In addition a moment (Mx) needs to be applied as the catenary wire is secured to the structure using a bracket and post type insulator which results in the load being applied up to 500 mm below the bridge. Refer to Figure 25 (a) and (b) for a typical fixed mid-point configuration. The value for this dimension may differ at each location and therefore needs to be determined in conjunction with Electrical Design.



5.5.2.4 Wind load on wire application (LC4)

Wind loads on the contact wire are simply applied to the drop vertical or mast at the node that has been modelled at contact wire height. Wind loads on the catenary wire are also applied to the drop vertical or mast but they are member loads located at catenary wire height plus 300 mm. The additional height allows for the depth of the insulators and attachments.

Wind loads on the wire always remain horizontal but can be applied in both the X and –X directions. The design engineer must determine which direction will produce the worst effect on the structure. Usually this direction will be easily determined by loading in the same direction as the radial loads. For structures where radial loads are applied in both directions the wind should be applied in the resultant radial load direction. If it is not obvious which direction the wind should be applied then additional load cases need to be developed. Figure 26 shows drop vertical and mast configuration and how the wind on wire loading is transferred as nodal and member loads in the Microstran model.





Figure 26 : Contact and catenary wind load modelling

5.5.2.5 Wind load on structure application (LC5, LC6 & LC7)

Wind loading is applied to the structure through a series of uniformly distributed loads (UDLs) on the members to represent wind pressure. Wind forces on kneebraces and electrical fittings can normally be disregarded. Determination of wind forces on the structural members was described in Section 5.4.2.5. These results are now applied to the structural model in the three design wind directions.



Wind on the structure in the X direction: Having determined wind loadings from Figure 19, for the appropriate structure size and type under design, apply these as UDL values to the masts and drop verticals in the structural model as force (Fx). With wind in the X direction the bridge will experience a drag force. To model the drag force the coefficient determined in Figure 19 is multiplied by the bridge length and the force Fx calculated is applied to a node located on the bridge. Alternatively the drag force may be applied as an axial UDL. An example of wind loading applied to part of a 300 SHS Portal is given in Figure 27.

The orientation that the wind load is applied is determined by the design engineer to produce the worst effect on the structure. Wind should be applied in the same orientation as the resultant radial loading.

Figure 27 : Wind on structure in X direction load modelling

Wind on the structure at 45o: Having determined wind loadings from Figure 20, for

the appropriate structure size and type under design, apply these as UDL values to the masts and drop verticals members in the structural model as force (Fx) and (Fz). With wind at 45o the bridge will experience a drag force from the (Fx) component while the (Fz) component is applied to the bridge members. To model the drag force the coefficient determined in Figure 20 is multiplied by the bridge length and the force (Fx) calculated is applied to a node located on the bridge. Alternatively the drag force may be applied as an axial UDL. An example of wind loading applied to part of a 300 SHS Portal is given in Figure 28.



Figure 28 : Wind on structure 45 degrees load modelling

Wind loads in the X component are applied in the same orientation as in the previous load case. Wind force orientation in the Z component of this load case is determined by the design engineer to produce the worst effect on the structure. Wind should be applied in the orientation that magnifies the effect of the moment created by the longitudinal movement of the overhead wiring.

Wind on the structure in the Z direction: Having determined wind loadings from Figure 21, for the appropriate structure size and type under design, apply these as UDL values to the masts, bridge and drop verticals members in the structural model as force (Fz). An example of wind loading applied to part of a 300 SHS Portal is given in Figure 29.

Wind force orientation in this load case is the same as the orientation determined by the design engineer for the Z component in the previous load case, the wind should be applied in the orientation that magnifies the effect of the moment created by the longitudinal movement of the overhead wiring.

Figure 29 : Wind on structure in Z direction load modelling

Care needs to be taken when applying all wind loads to the structure to ensure that the wind load effects are not cancelling out or reducing other forces. Special attention needs to be paid to ensure that the structural effects caused by the moment created due to longitudinal movement of the wiring is not negated by applying Z components of wind forces in the wrong orientation.



5.5.3 Load combinations

Once the primary load cases have been generated the load combinations are built by combining two or more primary load cases with relevant load factors to produce the desired combinations for design.

5.6 Design of structural steel members

For an overhead wiring structure to be considered acceptable the structural steel members that make up the structure must comply with the requirements of AS 4100 and ESC 330 for two limit state conditions:

Strength limit state; Serviceability limit state;

Design combination load cases have been developed for these two limit states in previous sections. These load cases are analysed by the software package providing ultimate design action and serviceability deflections for each member. The chosen steel sections are checked for section capacity, member capacity and combined action when the design loadings are applied as well as compliance with deflection limits. In addition to determining that the steel members meet all limit state requirements the design process is also about determining the most economical size structure. If a structure meets both strength and serviceability requirements and has additional capacity a smaller size structure should be investigated. The amount of work required to change the sections and some wind loading is minimal and should be undertaken as part of the design process. Microstran, which is currently used by RailCorp, is utilised in the following sections to demonstrate design methods and produce design output data. Other analysis packages will have similar features and outputs with many of the procedures described also being applicable.

5.6.1 Strength limit state design

There are two stages in the process to ensure the structure size selected for an OHWS meets the requirements for strength limit state design. They are:

Structural analysis; Steel design check;

These two processes are described in the following section and are supported by example menus and screenshots from Microstran.

5.6.1.1 Structural analysis

Strength combination load cases are processed using a non-linear analysis to determine ultimate design actions. To carry out this non-linear analysis all structural modelling, loading input and load combinations need to have been completed. The analysis is undertaken following the steps listed below:

Analysis step one: Select the Analyse tab on the top menu bar and move the highlighter to Check Inputs and select. This command launches a check of the model inputs to determine if the newly modelled structure has any fatal errors. All errors and warnings should be resolved before moving to the next step.

Analysis step two: Select the Analyse tab on the top menu bar and move the highlighter to Non-Linear… and select. A dialog box requiring the design engineer to select an analysis type for each load case will appear. Select all load cases for non-linear analysis. Both primary and combination load cases should be analysed so if any extraneous results are found in the combinations loads the primary load cases results can be viewed to determine where the error or incorrect loading has occurred. Select the OK and a new dialog box will appear which sets the non-linear analysis parameters of the software. Default limits are adopted, if they match the ones shown in Figure 30, and the OK button is selected.



Figure 30 : Default non-linear analysis parameters

Analysis step three: When convergence is achieved and the analysis completed view the results, both design action and deflection, to check that they are in the expected range for the size of structure being analysed.

Before accepting results from any analysis package the design engineer should know the order of magnitude that the expected results will be within. Results outside the expected range should be cause to investigate the modelling and loading before proceeding to the steel design check phase.

5.6.1.2 Steel design check

Design checking of the structural steel members in an OHWS is usually undertaken using an integrated steel design package. Design checking of the members can be undertaken by hand calculations but is very time consuming. For design engineers who have not used the integrated steel design package it is suggested that a set of hand calculations be undertaken for a simple structure and compare results to gain a better understanding of the package. The integrated steel design package used in Microstran is Limsteel. To have consistency in the design process a documented approach to user input variables, such as restraint types and effective length, have been agreed upon and are captured in the design steps as follows:

Design step one: Select the Design tab on the top menu bar and move the highlighter to Initialize Design Members - Linked and select. Refer Figure 31 (a) for menu format. Once launched a select cursor appears to allow the designer to choose analysed members to be linked together to form a design member. Using the cursor select members that form the mast and right click on the mouse to confirm acceptance of a linked design member. Each linked design member is assigned member type and design code which are accepted at this stage along with steel member default design data. Repeat this process until all members that require linking are initialized, e.g. other masts and bridges.



(a) initialize design members - linked

(b) initialize design members – not linked

Figure 31 : Initialize design members

The remaining members, e.g. kneebraces and drop verticals, also need to be initialized but as individual members, provided no additional nodes have been inserted. Select the Design tab on the top menu bar and move the highlighter to Initialize Design Members – Not Linked and select. Refer Figure 31 (b) for menu format. The process to initialize these members becomes the same as linked members.

Changes can be made to the default design data settings before the initializing steps begin so the design members are assigned default values relevant to the project. This is undertaken by selecting the File tab on the top menu bar and moving the highlighter to Configure – Steel Design – Default Code… and Default Design Data… and making amendments to the dialog boxes to suit the project. The default design data assigned to each member can be edited during the next step to customise as required.

Design step two: Select the Design tab on the top menu bar and move the highlighter to Design Data – Input/Edit… and select. Refer Figure 32 (a) for menu format. Once launched a select cursor appears to allow the designer to choose the linked or non-linked members to edit. The selected member is displayed dotted in the model and the first of four dialog boxes appear. The first dialog box has a heading Design Member and displays the member number that has been chosen and allows the designer to move between design members using the Previous and Next buttons.

When the member requiring editing is highlighted the OK is selected. Refer to Figure 32 (b) for dotted member and first dialog box. The second dialog box appears headed Member 1,2,3 (in this example) showing the currently selected design member and what analysed members have been linked in the previous step to form the design member. The designer chooses the type of member (steel) and design code (AS 4100) and selects OK. Refer Figure 33 (a) for the second dialog box.



(a) design data – input/edit menu

(b) design member

Figure 32 : Design data input

The third dialog box appears and consists of the default design data that was assigned to the members during initialization which is now edited for the member selected. The design engineer needs to input some data relevant to the member under review. The section type nominated in the default data needs to be checked and modified to UC for the mast if necessary and the steel grade of 300 needs to be entered if required. The Cantilever check box needs to be ticked to define the end of the member that is a cantilever, if any. In this example the end of the mast is the cantilevered end. The Sidesway check box does not need to be ticked as it is not required due to the non-linear analysis. When satisfied with all design data inputs for the member select the OK. Refer Figure 33 (b) for the third dialog box.

(a) member 1,2,3

(b) design data – steel member 1,2,3

Figure 33 : Typical portal mast design data

The fourth dialog box appears replacing the third and deals with restraint data for the selected member. The first two input columns deal with lateral torsional restraint of the top and bottom flange at each node. The three different flange restraint types that are available to nominate are:

L = Effective Lateral Restraint (solid green bars)

E = Elastic Lateral Restraint (dashed green bars)

N = No Restraint

For the mast of a typical portal structure the flange restraints are as depicted in Figure 34 (a) and (b). Node 1 has effective lateral restraint to both flanges as they are welded to the mast base plate. Node 2 has no restraint to either flange as it is only a modelling node for



the contact wire. At node 3 the kneebrace connects to the ‗bottom‘ flange providing elastic lateral restraint while no restraint is provided to the ‗top‘ flange at the node. Node 4 is the connection to the bridge which provides elastic lateral restraint to the bottom flange from the end plate connection. No restraint is provided to the top flange at this node location. For masts, the designer needs to understand which flange in their model is defined as the top flange and which is the bottom flange so that restraints are applied to the correct flanges.

Column buckling restraints nominate at what node locations sufficient restraint is provided in the XX or YY directions to prevent column buckling. The mast for a typical portal structure is depicted in Figure 34 showing column buckling restraints. In the member X-axis restraint is provided at node 1 by the base connection to the footing, node 3 by the kneebrace connection and at node 4 due to the bridge connection. A tick is placed in the ‗XX Col. Rest.‘ column, as shown in Figure 34 (a), at nodes that provide restraint. The nominated restraints are denoted in the visual display in Figure 34 (b) as red cones. Column buckling restraint about the member Y-axis is provided at node 1 by the base connection to the footing and at node 4 (by default with this software, it being the end of the member, but this node has been previously defined as the end of a cantilever in Figure 33(b)). The ‗YY Col. Rest.‘ column is ticked at these locations as shown in Figure 34 (a) and displayed as blue cones in Figure 34 (b).

(a) restraint data – steel member 1,2,3

(b) view restraints – steel member 1,2,3

Figure 34 : Typical portal mast restraint input

Effective length factors kx and ky depict the buckling mode that will occur between restraints and provide a factor to multiply the member length by for the design software to calculate the effective length. To determine these values Figure 4.6.3.2 in AS 4100 is used and for the mast of a typical portal structure a value of 1.2 is used for kx between the base and kneebrace connection and the kneebrace and bridge connection. The value adopted for ky is 2.2 between the base connection and the top of the mast.

When the restraint data dialog box is completed the design engineer accepts it by selecting OK. The software automatically highlights the next design member requiring the above dialog boxes to be completed and accepted. This process continues until all design members have been addressed.

Design step two provides design data and restraint data for a portal mast only. Completed dialog boxes for other structural components of overhead wiring structures are available in Appendix F.

Design step three: Select the Design tab on the top menu bar and move the highlighter to Design Load Cases – Steel Members… and select. Refer Figure 35 (a) for menu format. A dialog box listing all load case will appear. The purpose of this dialog box is to allow the designer to select which load cases will be used in the design check. Strength limit state load cases are chosen as indicated in Figure 35 (b) and the OK selected.



(a) design load cases – steel members

(b) select load cases for steel design

Figure 35 : Select design load cases

Design step four: Select the Design tab on the top menu bar and move the highlighter to Steel – (f/F) Check… and select. Refer Figure 36 (a) for menu format.

(a) steel - check

(b) selected members appear dotted

Figure 36 : Steel design check

Using the select curser choose members that are to be design checked and then right click and select OK. Members chosen appear dotted on the screen as shown in Figure 36 (b). If all members in the model require design checking then the Check All option should be used.

Once members are selected and accepted the design package carries out the design check of those members using the nominated design data, restraints and load cases.

Design step five: Review results and check that all members comply with the code requirements. To signify if the checked members are capable of meeting the code conditions for the load cases specified the results are given in terms of critical ratio. The critical ratio is an expression for the amount that the loading can be multiplied by and still comply with the code requirements. A value of one (1) or greater signifies that the member has sufficient capacity. Results of the design check can be viewed both graphically and in tabulated form.

Graphical results are a quick visual method to determine if the members are satisfactory. For each design member the critical ratio is displayed on screen over the graphics of the structure. From a quick inspection of the screen it can be determined if all members comply. An example of graphical results is given in Figure 37.



Figure 37 : Graphical results example

The results can also be produced in a summary or detail tabulated form. The detail results provide design outputs for each member and each load case and should be reviewed by the design engineer to ensure the results are consistent with what would be expected. An example of the summary form of results is given in Figure 38. The summary format gives more detail than the graphical output as it provides information on what load case caused the lowest critical ratio and what code condition governed.

Figure 38 : Tabulated results example – summary report

As part of the design process the most economical structure size needs to be determined. When modelling of the structure began the design engineer made a choice as to what size structure would be used based on span length and past experience. If after reviewing the results the critical ratio for the mast or bridge appears to be excessive (i.e.over-conservative) then the analysis and design may need to be undertaken again using a smaller structure size. Before this is done the serviceability check should be completed as these requirements may be the governing conditions in the design.

5.6.2 Serviceability limit state design

The serviceability requirements for an overhead wiring structure are achieved if the structure complies with the limits for static deflection specified in Table 6 and lateral contact wire deflection limit nominated by Electrical Design. The static deflection criteria are for new structures and are based on values that limit deflection in components of the structure to what is considered visually acceptable. The lateral deflection of the contact



wire due to structure deflection is limited to a value of 50 mm. This value is only one component considered by the electrical designer when ensuring pantograph security.

Two combination load cases have been developed that group relevant loadings to produce results for comparison with specified limits. These load cases are to be analysed along with the strength limit state load cases previously described.

Structure or Component Type

Maximum Vertical Deflection

Maximum Horizontal Deflection (In and Out of Plane)

Portals Span / 250 Height / 100 Single Mast N/A Height / 100 Cantilever Length / 75 (+ve)

Length / 500 (-ve) Height / 100

Drop Verticals N/A Length / 75

Table 6 : Static deflection limits

Application of the design limits to the results achieved is demonstrated for the two load cases as follows:

Static deflection limits are given in Table 6 and static deflections for the structure under investigation are obtained from load case 13. The length of each member is divided by the limit value given in Table 6 to obtain the deflection amount that each member must not exceed. The calculated amounts are compared with analysis results to ensure compliance. The deflection results can be obtained in graphical and tabulated format. An example of how static deflection results are checked is given in Figure 39.

(a) static deflection limits

(b) static deflection – tabulated results

Disclaimer

This document was prepared for use on the RailCorp Network only. RailCorp makes no wa



Bridge Vertical Deflection Limit 22730/250 = 91 mm Result = 25 mm Pass.

Mast Horizontal Deflection Limit (In & Out of Plane) 7700/100 = 77 mm In plane Result = 7 mm Pass. Out of Plane Result = 7 mm Pass.

DV Horizontal Deflection Limit (In & Out of Plane) 2500/75 = 33 mm In plane Results 14.2 – 6.9 = 7.3 mm Pass. Out of Plane Results -2.7 – 3.6 = 6.3 mm Pass.

(c) static deflection – graphical results

Figure 39 : Static deflection example

When determining the static deflection of a member the movement at both ends must be considered and a net value used for comparison with the deflection limits. This is especially relevant for drop verticals as deflection results are given in global coordinates and the bridge deflections need to be removed. Vertical deflection of the bridge is not usually affected as the masts do not experience significant compression. The masts are fixed at the base and deflection results can be read directly from the output.

The deflection limits given in Table 6 are applied to the final deflected shape, which must take into account any mast rake on single masts and cantilever structures and bridge or boom pre-camber on portals and cantilever structures.

Out-of-plane deflection limits are the most likely to be exceeded first as the members in overhead wiring structures are usually weaker in this direction. This is especially true for drop verticals as they transfer much of the out-of-plane loading in this load case. If the deflection limits are exceeded in the out-of-plane direction then the design engineer will need to investigate, with input from Electrical Design, if the initial assumption of 500 mm of longitudinal wire movement will actually occur. An actual amount of movement should be calculated and the loading recalculated. This adjusted loading may bring the deflection back within the specified limits.

Lateral deflection of the contact wire attached to an overhead wiring structure is limited to 50 mm by Electrical Design. If nodes have been placed at contact wire attachment points, as suggested in the section on modelling, then deflection values for the global X direction can be directly read from load case 14 results. The results can be presented in both tabulated and graphical form. In the tabulated form if the results output report for this load case is limited to nodes that have be designated as contact wire attachment points the output and check becomes very simple. A tabulated results output limited to contact wire node attachment points is shown in Figure 40.



Figure 40 : Contact wire deflection example - tabulated

All the contact wire lateral movements in this example are less than 50 mm so this structure would be deemed to meet the requirements of ESC 330. The same results can be viewed graphically which has the advantage of seeing how the structure deflection adds to the movement of the contact attachment point. A graphical representation of the above results is provided in Figure 41.

If the specified 50 mm contact wire deflection is exceeded the immediate reaction should not be to increase the structure to the next size. If all other strength and serviceability criteria are satisfied a number of solutions should be investigated before resorting to using a larger structure. A larger structure does not change the drop vertical size which is where a significant part of the deflection occurs.

The loading that produces the deflection is due to wind so the first option would be to define the orientation of the structure and determine if a reduction can be applied to the design wind speed. The wind pressure used is based on the assumption that the structure could be aligned in any wind direction so a direction multiplier Md = 1 has been used. Also confirm terrain category and shielding effects as this may also be able to be reduced so they are applicable to the specific structure. The reduction in wind loading due to the use of multipliers tailored to suit a particular structure location may bring the deflection to within specified limits.

As Electrical Design has specified the 50 mm limit as one component of pantograph security they may be able to increase the civil allocation under some circumstances. A discussion with the electrical designer should be held to see if additional movement can be allocated to the civil component.

All Deflections at Contact Wire

Attachment Points Are Less Than 50 mm

Therefore OK

Figure 41 : Contact wire deflection example - graphical



When the smallest structure size that meets both strength and serviceability requirements has been determined the footing size and type can now be determined. Footing design is addressed in Section 5-8 of this manual.

5.7 Anchor configurations

Overhead wiring is terminated at the ends of the wire runs by anchoring the wires to the mast of an overhead wiring structure that is usually being used to support and register the wire. In some circumstances a specific structure is allocated as the termination point. Tension in the wires being anchored can range from about 18 kN to 40 kN and usually is applied to the structure with the majority of the load in the out of plane direction which corresponds with the weaker direction of the mast being loaded. For this reason most terminations are connected to a guy footing so the structure size does not need to be excessive.

Guyed anchors are the preferred method for termination of wire runs as the majority of the load is transferred to the guy footing in the ground. The size of the mast supporting the termination arrangement is minimized and the deflection is controlled reducing visual impact. For a guy footing to be used sufficient room needs to be available behind the structure. Under some circumstances a guy footing is not possible so the mast must be free standing.

Two general types of anchor configurations exist

Fixed anchors; Moving anchors;

The type of anchor configuration to be used is specified by the electrical designer on the Electrical Loading Diagram by an arrangement drawing number. This arrangement is then conveyed onto the Structure Diagram by the civil design engineer. Anchor heights are also specified on the Electrical Loading Diagram. The anchor height given is above a reference track which is also given and is usually the track next to the mast to which the anchor is located but the civil design engineer should be aware that sometimes it refers to another track.

5.7.1 Fixed anchors

A fixed anchor is the termination of a wire run where no tensioning or movement is found in the anchorage. The most common use for this type of anchor termination is found associated with wiring of crossovers and termination roads such as sidings, storage yards and maintenance facilities. Fixed anchors are not always to be found in main line wire runs as fixed mid-points are often used, negating the need for fixed ends, although fixed anchors are often used to terminate bridle wires at fixed mid-points where a portal structure is not available to clamp the catenary wire. They may occasionally be used if a short run is required to meet configuration and layout needs in the main line situation.

A number of different configurations of the fixed anchor arrangement are used depending on the number of wires to be terminated, the orientation of the structure and the type of structure. The most common configurations are:

– Single wire termination with guy: A single wire termination is used to terminate the bridle wire at a fixed mid-point where no portal bridge is available to clamp the catenary wire. They are also used to terminate auxiliary feeders which have two fixed ends as they are not usually regulated. At fixed mid-point portals a single fixed anchor plate is often used to attach a guy to the structure in both directions to reduce mast deflection.



(a) electrical arrangement

(b) sample structure diagram

(c) photo

Figure 42 : Single wire fixed anchor termination

The anchor plate is attached by bolts to the flanges on the outside of the structure and extends beyond to allow attachments. This configuration allows a guy rod to transfer the tension from the wires to a guy footing as the mast is not strong enough to support the load freestanding. Figure 42 (a) depicts this anchor configuration showing typical electrical arrangement for a bridle wire anchorage at a single track fixed mid-point. Figure 42 (b) is a Structure Diagram showing the accepted notation and Figure 42 (c) a photo showing the arrangement installed.

The anchor arrangement is the same for single masts, SHS portals, double channel portals and double UB portals. The size of the anchor plate will vary with each structure type so a fitting number is used to specify the correct plate size for the structure.

– Double wire termination with guy: When a fixed end of an overhead wiring run is terminated the catenary and contact wires are attached to two separate fixed anchor plates on the structure. The contact wire anchor plate is attached to the outside face of the mast as this will prevent any clash that may occur with the kneebrace connection if the structure is a portal. The catenary wire anchor plate is attached to the inside face



of the mast. Due to the height of the catenary there will normally be no clash with the kneebrace connection. The anchor plates are placed on alternate sides of the mast to reduce the effects of twist produced by anchoring to the flange.



(c) photo

Figure 43 : Double wire fixed anchor termination

The anchor arrangement is the same for single masts, SHS portals, double channel portals and double UB portals. The size of the anchor plate will vary with each structure type so a fitting number is used to specify the correct plate size for the structure. Figure 43 (a) depicts this anchor configuration showing an electrical arrangement. Figure 43 (b) is a Structure Diagram showing the accepted notation and anchor plate details and Figure 43 (c) is a photo showing the arrangement installed

– Double wire termination without guy: When there is insufficient room or restrictions that prevent a guy footing from being installed a special structure called a free standing anchor mast (FSAM) is used. For fixed anchors a UC mast orientated with the strong axis aligned to the direction of the anchor wire is installed. The size of the section is nominated by the design engineer on the Structure Diagram with the steel fabrication and footing details provided by the standard drawing.

Anchor wires are connected to anchor plates that are bolted to the flanges on the face of the structure. The lines of anchor force pass through the mast centreline therefore



there is no eccentricity in the connection. Two anchor wires can be attached in this configuration as there are no tensioning weights to obstruct the lower connection. The mast needs to be raked to help reduce the visual effect of deflection. Free standing anchor masts are uneconomical and prone to high deflection and should be avoided where possible. Figure 44 (a) depicts this anchor configuration showing an electrical arrangement. Figure 44 (b) is a Structure Diagram showing the accepted notation and Figure 44 (c) a photo showing the arrangement installed.



(c) photo

Figure 44 : Double wire fixed anchor termination without a guy

5.7.2 Moving anchors

The majority of anchors used in overhead wiring design today are moving because the wiring system is regulated and requires the weight to provide constant tension and allow movement in the wire due to temperature variations. Most main line wire runs have a fixed mid-point and moving anchors at each end of the run. Short runs that do not have a fixed mid-point still require a moving anchor at one end.

A moving anchor has components that need to attach to the mast to prevent the weights from swinging and fouling structure gauge. To enable the fitting of these components the correct drilling types need to be specified when documenting the anchor location on the Structure Diagram. There also needs to be sufficient length in the single mast or portal leg to accommodate movement of the weights. Where shortened masts are used as



moving anchors the electrical designer should be made aware so checks can be made to determine that the weights will not be obstructed.

A number of different configurations of the moving anchor arrangement are used depending on the number of wires to be terminated and the orientation of the structure. These configurations are:

– Single wire termination with guy: One use of a single wire termination is when the catenary and contact wire have been combined at an equalizing plate and a single wire goes to anchor. This is often the situation with a crossover wire run as the tensions in the catenary and contact wires are very similar. When masts are placed between tracks with tight clearances single weight terminations are used to keep the weights within the width of the leg.

electrical arrangement


(c) photo

Figure 45 : Single wire moving anchor termination

When the termination is to a single mast or the leg of a SHS portal, that is supporting the overhead wiring, the orientation of the UC is such that the web is available for attachment of the wire and the loading is applied to the centre of the member. This type of attachment requires a guy rod to be connected as the structure has insufficient strength. The anchor fittings are bolted together with the web sandwiched in between. The weight stack sits in front of the mast and adds little if anything to the effective width of the mast



so there is little if any effect on clearances. A guide rod is provided to prevent the weights from swinging.

Figure 45 (a) depicts this anchor configuration showing an electrical arrangement. Figure 45 (b) is a Structure Diagram showing the accepted notation and the anchor plate details and Figure 45 (c) a photo showing the arrangement installed.

When this type of arrangement is required to be attached to a double channel or double universal beam portal the same anchor fittings are used but are separated by the width of the mast and individually bolted to the web of the channels or beams on both sides of the battened mast.

– Double wire termination with guy: The most common anchor configuration used would be the moving anchor with two sets of weights. To provide separation of the weights anchor plates are bolted to the inside and outside face of the mast and the wires are terminated to the anchorage points they provide. Moving anchor plates are fabricated with special lugs that allow the tensioning system to be attached.



(c) photo

Figure 46 : Double wire moving anchor termination

The anchor plates are attached to the mast so the lugs are facing the incoming terminating wires. Construction staff can determine from the structure diagram the side of the structure on which the wires are to terminate - it is opposite to the side (Sydney or Country) nominated for the guy footing.



The contact wire anchor plate is attached to the outside face of the mast as this will prevent any clash that may occur with the kneebrace connection. The catenary wire anchor plate is attached to the inside face of the mast. The height of the catenary will avoid a clash with the kneebrace connection. The anchor plates are placed on alternate sides of the mast to provide separation of the weight stacks. The drilling details remain the same as for a fixed anchor reducing the number of drilling types and making the plates interchangeable

The anchor arrangement is the same for single masts, SHS portals, double channel portals and double UB portals. The size of the anchor plate will vary with each structure type so a fitting number is used to specify the correct plate size for the structure. Figure 46 (a) depicts this anchor configuration showing an electrical arrangement. Figure 46 (b) is a Structure Diagram showing the accepted notation and the anchor plate details and Figure 46 (c) is a photo showing the arrangement installed.

– Single wire termination without guy: When there is insufficient room or restrictions that prevent a guy footing being installed a special structure called a free standing anchor mast (FSAM) is used. For a single moving anchor termination a UC mast orientated with the strong axis aligned to the direction of the anchor wire is installed. The size of the section is nominated by the design engineer on the Structure Diagram with the steel fabrication and footing details provided by the standard drawing.

The Anchor wire is connected to an anchor plate that is bolted to the flanges on the face of the structure. Only one wire can be anchored with this configuration as the weight stack is positioned at the centre of the mast. The mast needs to be raked to help reduce the visual effect of deflection. These structures are uneconomical and prone to high deflection and should be avoided where possible. Figure 47 (a) depicts this anchor configuration with a Structure Diagram showing the accepted notation and the anchor plate details and Figure 47 (b) is a photo showing the arrangement installed.

(a) sample structure diagram

(b) photo

Figure 47 : Single wire moving anchor termination without a guy



– Double wire termination without guy: When there is insufficient room or restrictions that prevent a guy footing being installed and a double moving anchor is required a special structure called a boxed free standing anchor mast (Boxed FSAM) is used. To make use of standard moving anchor plates and to keep the two sets of weights separated it is necessary to orientate the mast in the weak axis to provide flanges to attach the anchor plates. To provide the strength in the direction of the loading the weak axis of the UC needs to be strengthened by adding plates to the front and back and thus boxing in the section. The steel fabrication and footing details are provided by the standard drawing.

The Anchor wires are connected to anchor plates that are bolted to the flanges on the side of the structure. The mast needs to be raked to help reduce the effect of deflection. These structures are very uneconomical and should be avoided where possible. Figure 48 (a) depicts this anchor configuration showing a Structure Diagram with the accepted notation and anchor plate details. Figure 48 (b) is a photo showing the arrangement installed.

(a) sample structure diagram

(b) photo

Figure 48 : Double wire moving anchor termination without a guy

5.7.3 Special anchor configurations

Due to the wide variety of structures and numerous track configurations there are some locations where the standard anchor configurations do not work. In these situations variations on the standard arrangements are used to produce an anchorage that makes use of the standard electrical fittings and anchor plates with minimal change to structures. Some of the more frequently used special anchor configurations are:

– Tied anchor structures: In multiple track configurations where track centres are sufficient for a mast to be placed between two tracks but not sufficient clearance to allow side-by-side weight stacks, a special tied anchor arrangement is used. This arrangement takes the contact wire and terminates it as a single moving anchor arrangement to a single mast located a short distance in front of the main anchor structure. This allows the weight stack to remain within the width of the structure or very nearly so. The single mast is cut short to allow the catenary wire to continue over the top of it and terminate as another single moving anchor to the mast of the main anchor structure.



Anchoring heights may need to be discussed with electrical design to ensure that the pulley system for the catenary does not foul the top of the contact wire anchor mast as the weight of the arrangement causes some local sag in the catenary. It is for this reason the mast separation is kept to a minimum.

As both structures are being loaded in the weak direction and are not capable of carrying the anchor loads as free standing masts they require guy rods to transfer the loading to a guy footing. The contact anchor mast is tied back to the main anchor structure mast by placing fixed anchor plates on each of the four flanges at the contact anchor height and connecting them with rods and turn buckles. The tie is thus via the outsides of the masts, which is to enable the catenary weight stack support rod to pass between the tie rods. From the main anchor structure mast at contact anchor height two rods connect to the guy footing. (Alternatively an additional web-mounted guy anchor plate could be attached to the main anchor mast to enable just a single guy rod to connect to the guy footing for the contact wire anchor.) The guy arrangement for the catenary anchor is the same as for a single weight stack. Figure 49 (a) shows an electrical arrangement and Figure 49 (b) is a photograph of a tied anchor arrangement.


(b) photo

Figure 49 : Tied anchor termination

Footings for tied anchor structures may be a combined footing that contains two pedestals, one for each structure, sitting on one large footing. The structures would be 1 metre apart. A combined footing needs to be specially detailed to avoid construction difficulties. (Alternatively a separation of 2 to 2.5 metres between the structures may be adopted to enable separate footings to be constructed using standard details.) The two structures in a tied anchor arrangement are always identified as separate structures and given different structure numbers.

– Anchorage to a cantilever mast structure: Cantilever masts are not usually used for termination of wire runs for two reasons. Firstly the additional radial loading created by the anchor has significant effect on the static deflection of the structure which is usually already the controlling factor in the design. Secondly the standard practice of bolting anchor plates to the flange of the structure becomes difficult as specialized fasteners are required. Welding of the plates would be one practical solution but not always considered viable as it removes the ability to adjust the height in the field if it becomes necessary.



For these reasons anchoring to a cantilever structure is avoided but in some situations when it does become necessary the problems can be overcome if consideration is given to the two difficulties. If deflection from the additional radial load becomes a controlling factor it can be overcome by specifying a structure that has a stronger mast such as the 300 SHS Light Cantilever Mast or a 300 SHS Cantilever Mast.

Fixed or moving anchor plates are attached to the faces of the SHS mast using Lindapter Hollow-Bolts which allow anchor height adjustment by redrilling if it becomes necessary. Modifications to the electrical fittings (anchor plates) will be required as the Hollow-Bolts require oversize holes. This information can be added to the Structure Diagram.

Footing size for the nominated cantilever mast should be checked for the additional lateral loading due to the anchor attachment. If the loading exceeds the capacity of the footing a larger or deeper footing will need to be specified.

If the need arises to develop a special anchorage arrangement it should be constructed from standard anchor plates and fittings if possible so special plates and fittings are not required to be introduced into the overhead wiring system. Electrical Design will need to be involved as anchor arrangements are their responsibility.

5.8 Design of footings

Determining the size of the structure is only one of the design elements of an overhead wiring structure. The footing also needs to be designed in order to complete the structural design. An overhead wiring structure footing can be designed by one of the following methods:

Standard footing design; Nominated footing depth design; Site specific footing design;

5.8.1 Standard footing design

For each standard overhead wiring structure there is a corresponding standard footing drawing that provides footing construction details including the depth to which it should be constructed for different foundation conditions. A qualified geotechnical engineer is to be on site at the time of construction to confirm the foundation material and recommend a depth in accordance with the tabulated design depth provided on the standard footing drawing for the particular structure under consideration. Figure 50 is a typical footing depth table showing both regular and pile footing depths for different foundation materials.

This method of determining the footing depth is the most frequently used for new construction as geotechnical site investigation can be expensive as footings are spread over large distances which would require boreholes and report for each structure or footing location.



Figure 50 : Typical standard footing depth table

The disadvantage with this method of footing design is that the required depth of footing is not determined until construction is underway. This problem is easily overcome as the design of the regular and pile footing reinforcement is such that it can be adjusted during construction. As can be seen in Figure 51 the reinforcement in the base of the regular footing consists of a top and bottom half which can be slid in or out to the required depth. Provided the minimum amount of lap is maintained, for the vertical bars in all faces, at the maximum footing depth one size cage can be used for all depths of footing. The number of horizontal ties is adjusted as necessary. The pedestal reinforcement remains unchanged regardless of the footing depth.

Figure 51 : Typical regular footing reinforcement

When constructing a pile footing the reinforcing cage can be ordered to the maximum length likely to be needed and cut to length to suit the depth of footing required when the hole is bored and the foundation material is known. Figure 52 depicts a typical pile footing reinforcement detail. It should be noted that the pile depth on a sloped embankment is measured below the point where the pile has two metres of horizontal soil cover. The



pedestal reinforcement remains unchanged regardless of the footing depth but has different minimum height requirements for level and sloped ground.

The civil design engineer has a responsibility when utilising the standard footing design method to ensure that the standard footing capacity is not exceeded. The structure size is chosen based on steel section design (described earlier) and then a check is done to ensure that the allowable footing loadings, for the nominated structure, do not exceed the standard structure footing allowable loads given in Table 7. Using reactions determined from Load Cases LC15, LC16 and LC17 a comparison between these values and the maximum allowable loading for the footing types under investigation is undertaken, this process ensures that standard footing capacities are not exceeded.

The maximum allowable footing loads given in Table 7 have been applied at the underside of the pedestal for determination of footing depths given on the standard drawings. The design engineer must increase the moments obtained from the structural model to account for the height of the pedestal. I.e. the horizontal forces Fx & Fz are multiplied by the pedestal height and the moments obtained are added to the corresponding Mz & Mx values.

Figure 52 : Typical pile footing reinforcement



Structure Type

Maximum Allowable Horizontal Force FX or FZ (kN)

Maximum Allowable Moment MZ (kNm)

Maximum Allowable Moment MX (kNm)

PP2/HP2 Mast 10 90 90 PP3/HP3 Mast 10 140 140 200 SHS Portal 20 80 80 250 SHS Portal 20 120 120 300 SHS Portal 30 180 180 250 SHS Cantilever Mast 25 150 150 300 SHS Light Cantilever Mast

40 220 220

300 SHS Cantilever Mast 50 250 250 300DC Portal 30 150 100 380DC portal 30 210 170 FSAM 310 UC 137 or smaller

45 320 320

FSAM 310 UC 158 60 400 400

Table 7 : Maximum allowable footing loads

The values in Table 7 consist of Horizontal Forces (H), in the X and Z direction, and Moments (M), about the X and Z axis, and represent the maximum allowable load that the documented footing for a particular structure type can resist. Moment values given represent 80% of the permissible stress of the steel section and are the allowable design loadings that have been used to determine the required footing depths for different foundation types on the standard footing drawing. Note, both regular and pile footings are considered to resist applied forces and moments predominantly through lateral bearing.

When checking the capacity of a regular footing it needs to be assessed in two directions, LC 15 and LC 17, as these footings have two distinct load bearing faces due to being square or rectangular in section. If the footing is suitable in these two directions a final check is made to ensure the resultant of LC15 and LC17 does not exceed the value of LC16. This check for loading at 450 is the final confirmation of the footing‘s suitability.

For a pile footing the maximum moment (M) value in Table 7 along with horizontal force (F) can be applied in any direction and all three load cases, LC15, LC16 and LC17 should be compared to the allowable load. The footing design is complete when the applied loadings are less than the allowable for all load cases.

The third type of standard footing available for use is the rock footing. Use of this footing is limited due to suitable footing locations as explained in Section 4.3 and 8.2.10. As the footing can only be used in class I and II shale or sandstone the detailing is the same for all footing locations for a particular structure size. Capacity checks similar to those described for the regular footing (i.e.comparison of applied forces and moments with allowable footing loads in Table 7) are required to be undertaken by the civil design engineer.



Figure 53 : Typical rock footing detail

Guy footings need to be checked for stability before a particular size is specified on a Structure Diagram. The three guy footing sizes available satisfy stability requirements provided the maximum allowable loads given in Table 8 are not exceeded. These loads represent the total anchor loads of common regulated overhead wiring conductor systems. To achieve similar horizontal and vertical loads the guy footing is placed by default the same distance from the mast as the largest anchor height is above the base plate. This will achieve a 45o angle to the higher anchor rod. To ensure that excessive overturning moment is not produced the pedestal height is limited to a maximum of 1000mm.

If necessary it is acceptable for the guy footing to be placed further than the default distance from the mast. But if, due to site factors, a guy footing needs to be placed closer than the default distance, with the result that the guy rod angle is steeper than 45o, the applied vertical force may exceed the allowable - this would require a stability check and possibly the selection of a larger standard guy footing for that structure.

Guy Type Maximum Allowable Horizontal Force (kN)

Maximum Allowable Vertical Force (kN)

G1 Guy Footing 40 40 G2 Guy Footing 56 56 G3 Guy Footing 66 66

Table 8 : Maximum allowable guy footing loads

The guy footing sizes and respective capacities are grouped to accommodate the range of conductors and tensions used in current regulated systems. Table 9 gives an indication of what conductor systems and maximum total tensions can be used with each guy footing. It is the responsibility of the civil design engineer to specify a guy footing size that ensures that the allowable footing loads are not exceeded.

Guy Type

Overhead Wiring Conductor System

System I.D. No.

Catenary Wire Contact Wire

Size (mm

2)

Maximum Tension (kN)

Size (mm

2)

Maximum Tension (kN)

G1 Guy 10 165 18.50 193 18.00



4 & 6 270 19.00 5 270 19.43 2x137 19.43 1 327 16.50 193 16.50

G2 Guy

2 & 3 270 30.00 2x137 25.00 9 270 23.10

193 18.00 8 327 26.40 7 510 34.60 15 2x165 30.80 2x137 25.00

G3 Guy 12 2x270 40.70 2x137 25.00

Table 9 : guy footings and conductor system

The system identification number in Table 9 represents the different overhead wiring conductor systems available for use in regulated overhead wiring within the Sydney metropolitan rail network.

5.8.2 Nominated footing depth design

If geotechnical information is available at or near the location of a structure footing then the civil design engineer should specify the depth of footing required. The depth is determined by identifying the foundation material type from the geotechnical report and comparing it with the range of material available on the standard footing drawing for the structure size under consideration. Once a suitable material type has been determined the depth of footing can be chosen from either the regular or pile footing type column depending on the type of footing specified at the location.

The chosen footing depth needs to be included on the Structure Diagram so that construction staff know what is required. This information is placed next to the footing opposite the reduced level of the pedestal and setting out coordinates, and should state the foundation material parameters (e.g. Cu = 50 kPa) along with a footing depth. For a regular footing a dimension from the top of the footing to the underside should be provided. A pile footing should also be dimensioned and include any additional length needed to achieve the effective pile depth given in the standard footing table. Figure 54(a) and Figure 54(b) provides examples of required documentation on a Structure Diagram.

(a) regular footing documentation

(b) pile footing documentation

Figure 54 : Nominated footing depth design

With the nominated depth footing design the civil design engineer must also undertake the same design checks for the capacity of the particular footing under investigation as would be done for a standard regular or pile footing as required in Section 5.8.1. Footing depths nominated on a Structure Diagram take preference over depths given on a standard footing drawing.

The advantage of this method of footing design is that the reinforcing cage size can be finalised before construction and the amount of excavation is known. No on site



geotechnical advice at time of construction is required. These advantages can only be achieved when geotechnical data is available. It becomes uneconomical to obtain this information specifically for the purpose of providing footing depths on the Structure Diagram.

5.8.3 Site specific footing design

For some structures it is not possible to use a standard footing design as the structure loads or foundation conditions fall outside the allowable loading range given in Table 7 or the soil/rock parameters given on the standard footing depth table on the structure drawing.

When these types of structures occur it is the responsibility of the civil design engineer to design the footing using a recognised method of analysis. If a site specific footing design is required due to the allowable loads in Table 7 being exceeded then not only should a new depth of footing be determined but the capacity of the footing reinforcement and hold down bolts need to be checked.

Note, OHWS regular and pile footings are considered to resist applied forces and moments through lateral bearing only. Applied vertical forces are usually comparatively minor, so bearing capacity of the base is not usually a critical factor. Spread footings are not used on new OHWS due to the relatively high applied moments and the vulnerability of spread footings to interference by nearby excavations and other works during the life of the structure.

A site specific footing design will require geotechnical parameters so a footing depth can be determined and documented on the Structure Diagram similar to nominated footing depth design documentation shown in Figure 54 (a) and (b). Actual geotechnical values used need to be provided.

If geotechnical data is not available the design will need to provide a range of depths for different founding materials similar to a standard footing design shown in Figure 50.

Where possible the standard footing design documented on the Railcorp standard drawing should be used with the depth increased accordingly and shown on the Structure Diagram. If this is not possible due to loading or some site requirement a site specific footing will need to be produced and documented in accordance with Section 8.4. The use of standard footings is preferred by RailCorp.

5.9 Feeder and switching structures

To supply and control power into the overhead wiring system and for the subsequent management of distribution of the power within the system a number of feeding and switching points are required. Structures are required to provide support for cables and equipment at these locations. Design of the supporting structures is the responsibility of the civil designer with configuration requirements and cable and equipment loading being provided by the electrical designer.

These structures generally perform two different functions, both having different design requirements. Designations of these structures are:

Feeder structures; Switching structures.

5.9.1 Feeder structures

At locations where power is fed into the overhead wiring system, high voltage cables are required to be run from ground level beside the track, up to some point close to the



catenary wire being fed above a particular track. The preferred method of achieving this is through the use of an overhead wiring structure.

The feeder cables have a considerable diameter and weight that provide additional dead load to the structure and increased surface area for wind load to transfer to the structure. OHW equipment such as insulators and their support brackets also add weight and wind loading area to the structure.

The majority of feeder structures make use of the mast and/or bridge to attach the cables to reach their destination, but at some locations where multiple tracks are present, access to the structure through the use of fixed ladders and walkways is required so inspection and maintenance can be undertaken outside of possession or while one set of tracks is still operational. The requirement for access to these structures is determined by the Electrical Maintenance Engineer. Feeder structures that require access are complex due to live loading requirements and are therefore dealt with separately.

5.9.1.1 Feeder structures without access

When provision of access is not required an existing or proposed overhead wiring structure can be used as the feeder structure if appropriate. In some circumstances a new structure solely for feeding purposes is designed and installed. A single mast can be used to feed a single track if located less than 4m away from the mast as shown in Figure 55 (a). The cables are typically clamped inside the section limiting wind loading effects but the weight of the cables, insulators and their supports need to be considered.

When multiple tracks need to be fed the feeder cables are attached to the structure by a bracket system clamped to the mast and bridge so the cables are arranged on the outside of the structure. This arrangement allows the cables to be bent through the 700 mm to 1200 mm typical bending radius to change direction from vertical on the mast to horizontal along the bridge. Figure 55 (b) shows a multiple track feeder structure arrangement.

The feeder cables used typically have 400 mm2 copper core X.L.P.E (cross linked poly ethylene) insulated with 90 mm2 copper screen, PVC & HDPE sheathed and weighs about 5.6 kg per metre with a diameter of 47mm. These parameters along with the weight and size of other equipment should be confirmed with the electrical designer before applying them to a design situation.

(a) single mast feeder structure

(b) portal feeder structure

Figure 55 : Typical feeder structure arrangements



Regardless of the configuration used, feeder cables and equipment add loading to the structure which needs to be considered over and above those discussed in Section 5.4. A number of the design load cases used for overhead wiring structures will need to have additional loading applied to simulate the effects of the feeder cable and equipment. These load cases are:

Load case 1: Self weight of the cables of 5.6 kg per metre should be added to this load case as a vertical nodal load on the mast and a member loading on the bridge. In addition to these direct loads the effects caused by their attachment offset needs to be considered. A moment needs to be applied at each attachment point to represent the loads produced. Cabling is usually attached symmetrically about one face of the mast and should therefore cancel out the moment effects in the out of plane direction. On the bridge the number of feeder cables reduce as each track is fed. Depending on the arrangement of cables the moments may not always balance. Typical cross sections of the mast and bridge showing cable arrangements can be found in Figure 56 (a) and (b) respectively.

(a) typical mast cross section

(b) typical bridge cross section

Figure 56 : Cable arrangement for a typical portal feeder structure

Weight of the insulators and their attachment supports also need to be added in this load case. Details of the offset from the mast or bridge centreline are needed so an appropriate moment can be applied. These details along with confirmation of cable type and arrangement need to be obtained from the electrical designer.

Load case 5: For wind on feeder cables in the X direction only cables that are attached to the structure, and exposed beyond the structural elements that have already contributed to wind loading, have their wind load added in this load case. As seen in Figure 57 (a) only two of the four mast cables would need to have their contribution to wind loading added. Each cable exposed to the wind produces a member load of 0.05kN/m applied in the X direction with the same orientation as the wind load on the structure. As shown in Figure 57 (b) each cable on the bridge is exposed to a frictional drag force of 0.012kN/m, which is applied in the same direction as the bridge frictional drag force.



(a) wind in X direction on mast

(b) wind in X direction on bridge

Figure 57 : Typical load case 5 wind loading, feeder structure without access

The design engineer must also consider the wind loading, in the X direction, on insulators and attachment brackets and make suitable additions to the structural model and loadings to represent their effects.

Load case 6: Loading due to wind at 45o on the mast feeder cables is applied to the model in the X & Z direction. Loading is calculated by multiplying the full cable wind load, 0.05 kN/m (wind perpendicular to cable), by 0.707 giving a loading of 0.035 kN/m which is applied to the cables in both directions. As the wind is at 45o the design engineer will need to determine if any shielding should be applied. For the feeder cable configuration given in Figure 57 (a) no shielding would be applied.

Bridge feeder cable loadings under 45o wind are determined by multiplying the loads obtained in load cases 5 and 7 by a factor of 0.5 and applying the values in this load case. The 0.5 factor has been obtained from recommendations in AS/NZS 1170.2 Clause E2.1 (b) as the cables are a round cylindrical shape treated as a member inclined at 45o to the wind direction. Therefore Ki = 0.5.

The calculated loadings are to be applied in the same direction as 45o wind loading on the structure. An allowance should be made by the design engineer for wind loading on the insulator and attachment brackets.

Load case 7: For a typically configured feeder structure with the mast and bridge sections as shown in Figure 58 (a) and (b) the wind loading on the feeder cables in the Z direction will act fully on the first cable and be reduced by a shielding factor of 0.2 for all subsequence cables.

On the mast a member load of 0.05 kN/m is applied to the structure plus 0.01 kN/m for each cable shielded by the first cable. For cabling on the bridge a member load of 0.06 kN/m is applied to the structure plus 0.01 kN/m for each cable arranged behind it. All loads are applied in the Z direction with the same orientation as the structure wind load.

The design engineer must also consider the wind loading, in the Z direction, on insulators and attachment brackets and make suitable additions to the structural model and loadings to represent their effects.



(a) wind in Z direction on mast

(b) wind in Z direction on bridge

Figure 58 : Typical load case 7 wind loading, feeder structure with out access

The wind loading values given in the load cases above have been determined using a 47 mm diameter feeder cable, with z = 5 m for the mast, z = 7.5 m for the bridge and normal exposure conditions. Calculations for the values used are presented in Appendix E. Should the cable size, wind height or exposure condition be different new values are to be calculated. The design engineer should confirm that the feeder arrangements being used at the location are the same as described for the load cases above and make adjustments as required.

5.9.1.2 Feeder structures with access

When a feeder structure requires access, two standard structures are available for use as their configuration is suitable for access ladders and walkways. The 300 Double Channel Signal or Feeder Structure and the 380 Double Channel Portal are the only two standard structures that can provide access to the feeder cables across the bridge of the structure. Figure 5.49 shows a typical feeder structure with access.

Figure 59 : Typical feeder structure arrangement with access

A feeder structure with access would usually also be supporting overhead wiring to make efficient use of the structure. The design process used is similar to an overhead wiring



structure with loadings added to some of the primary load cases. These load cases and loadings are as follows:

Load case 1: Self weight due to the ladder, ladder cage, walkway and hand rails are added to the model in this load case. The values of these loadings and how they are applied to the model is covered in Chapter 6.

Cable self weight of 5.6 kg per metre should be added to this load case as a vertical nodal load on the mast and a member loading on the bridge. In addition to these direct loads the effects caused by their attachment offset needs to be considered. A moment needs to be applied at each attachment point to represent the loads produced. Cabling is usually attached to both sides of the mast and should therefore cancel out the moment effects. On the bridge the number of feeder cables reduce as each track is fed. Depending on the arrangement of cables the moments may not always balance. Typical cross sections of the mast and bridge showing cable arrangements can be found in Figure 60 (a) and (b) respectively.

(a) typical mast cross section

(b) typical bridge cross section

Figure 60 : Cable arrangement for typical portal feeder structure with access

Load case 2: As the structure is trafficable live loading in accordance with AS 1657 needs to be applied to the area of walkway provided. Loading and modelling of the structure for live trafficable loads is covered in Section 6.

Load case 5: For wind in the X direction with a typical mast configuration as shown in Figure 61(a) loading on the feeder cables will be 0.05 kN/m for the first cable and be reduced by a shielding factor of 0.2 giving a value of 0.01 kN/m for all subsequent cables. As shown in Figure 61 (b) each cable on the bridge is exposed to frictional drag force of 0.012 kN/m which is applied in the same direction as the bridge frictional drag force.



(a) wind in X direction on mast

(b) wind in X direction on bridge

Figure 61 : Typical load case 5 wind loading, feeder structure with access


Load case 6: Loading due to wind at 45o on the mast feeder cables is applied to the model in the X & Z direction. Loading is calculated by multiplying the full cable wind load, 0.05 N/m (wind perpendicular to cable), by 0.707 giving a loading of 0.035 N/m which is applied to the cables in both directions. As the wind is at 45o the design engineer will need to determine if any shielding should be applied. For the feeder cable configuration given in Figure 6 (a) shielding would be applied to cables 3 to 6 on the lee side of the mast.

Bridge feeder cable loadings under 45o wind are determined by multiplying the loads obtained in load cases 5 and 7 by a factor of 0.5 and applying the values in this load case. The 0.5 factor has been obtained from recommendations in AS/NZS 1170.2 Clause E2.1 (b) as the cables are a round cylindrical shape treated as a member inclined at 45o to the wind direction. Therefore Ki = 0.5.


Load case 7: For the typical mast cable configuration shown in Figure 6 (a) only four of the twelve cables, cables 1 and 6 on each side of the mast, will need to have their contribution to wind loading added to the structural model. Each of these four cables produce a member load of 0.05 N/m applied in the Z direction. The typical bridge cable configuration shown in Figure 6 (b) requires all twelve cables to contribute as the spacing between the two banks of cable is large enough to prevent shielding. For each cable a member load of 0.06 N/m is applied to the structure plus an appropriate moment to represent the lever arm.



(a) wind in Z direction on mast

(b) wind in Z direction on bridge

Figure 62 : Typical load case 7 wind loading, feeder structure with access



Combination load cases for strength and serviceability will be different from those used for overhead wiring structure as combinations for live loading and wind need to be considered as the structure has become trafficable. The combinations and factors applicable to a feeder structure with access supporting overhead wiring are covered in Section 6.

5.9.2 Switching structures

To allow electrical sectioning of the overhead wiring network, switches are required at specified locations. A switch location involves switching mechanism and cabling and/or aerial feeder wires which all add loading to the structure supporting the equipment. These loadings need to be considered when designing the supporting structure.

Switches are normally attached to single masts or the mast of a portal structure but are limited to two per mast due to their size limitation. If a switch location requires a greater number of switches than can be accommodated on the mast, then a switching frame independent of the overhead wiring structure is typically provided. The location, mounting configuration and structure type required for a switch location is determined by Electrical Design.

5.9.2.1 Mast mounted switches

A single mast will typically have one switch attached as it can only be used to switch an adjacent track. If a single mast is located between two tracks both could potentially be switched form the single mast. To switch further tracks a portal bridge is required to



support the switching cables. Switches mounted on single masts or portal structure masts have the same configuration and are located on the Sydney and/or Country side of the mast. The switch operating lever is mounted typically at a height of 1050 mm (+50 mm, -100 mm) above the switch operating platform which is positioned between ground level and rail level. The switch mechanism is located further up the mast at catenary height and the two pieces of equipment are connected by a rod. If the operating platform is located in close proximity to the live traffic a handrail to provide a physical barrier may be required. Typical mast mounted switches can be seen in Figure 63.

On a single mast, aerial feeder wires from the switch mechanism are suspended by a gallows arrangement to reduce loading on the switch and enable it to reach the overhead wiring. Excessive loading on a switch can cause the blades to go out of alignment and malfunction. This arrangement can be seen in Figure 63 (a) and (b). When a portal structure is used the cabling from the switch mechanism, located on the mast, to the track overhead wiring is supported by the bridge. The cable arrangement and attachment on the bridge are similar to that for a feeder structure as can be seen in Figure 63 (c).

The switching cables are normally the same 400mm2 copper cables mentioned in Section 5.9.1.1. Cable parameters along with the weight and size of other equipment should be confirmed with the electrical designer before applying them to a design situation.

To account for the additional loading created by the switch equipment and cabling, the following additions to the overhead wiring structure load cases need to be implemented.

Load case 1: Self weight of the switching gear should be added to this load case as a vertical nodal load on the mast. For a portal structure a member loading on the bridge to represent the cabling needs to be applied. In addition to these direct loads the effects caused by their attachment offset needs to be considered. A moment needs to be applied at each attachment point to represent the loads produced. Cabling is usually attached to both sides of the bridge but reduces as each track is switched. Depending on the arrangement of cables the moments may not always balance.

Weight of the insulators and their attachment supports also needs to be added in this load case. Details of their offset from the mast or bridge centreline are needed so an appropriate moment can be applied. These details along with confirmation of cable arrangement need to be obtained from the electrical designer.



(a) typical simple mast switch

(b) typical mast mounted switch photo

(c) typical portal switch structure

Figure 63 : Typical mast mounted switches

Load case 5: As seen in Figure 63 the switch gear and rod will generate wind loading in the X direction that needs to be determined by the design engineer and applied to the structure. Wind loading on any cabling attached to the mast is insignificant and can be ignored for switch structures as the majority is shielded. For cable on a portal bridge that is exposed to frictional drag a load of 0.012 kN per metre should be applied in the same direction as the bridge frictional drag force.




Load case 6: Loading due to wind at 45o on the mast switching components is applied to the model in the X & Z direction. Loading is calculated by the design engineer taking into consideration aerodynamic shape factor of the equipment for wind in a particular direction. As the wind is at 45o the design engineer will need to determine if any shielding should be applied.

Bridge switching cable loadings under 45o wind are determined by multiplying the loads obtained in load cases 5 and 7 by a factor of 0.5 and applying the values in this load case. The 0.5 factor has been obtained from recommendations in AS/NZS 1170.2 Clause E2.1 (b) as the cables are a round cylindrical shape treated as a member inclined at 45o to the wind direction. Therefore Ki = 0.5.


Load case 7: Wind loading in the Z direction for the mast equipment and cabling can be ignored as the majority is in line with the mast and does not contribute significantly to loading. For a typically configured portal switching structure shown in Figure 63 (c) the bridge sections will be similar to a feeder structure shown in Figure 58 (b). Therefore wind loading on the switching cables in the Z direction will act fully on the first cable and be reduced by a shielding factor of 0.2 for all subsequent cables. For each metre of cabling on the bridge a member load of 0.06 kN is applied to the structure plus 0.01 kN/m for each cable arranged behind it.



Mast mounted switches also require an operator‘s platform which is typically configured as detailed on drawing EL 0491331. The design of the mast pedestal height above ground should make allowance for the attachment of this platform.

5.9.2.2 Switching frame

A switching frame is an independent construction consisting of a frame that supports a multiple bank of switches. The frame is located near an overhead wiring structure so the cables can be connected to the overhead wiring via the frame in much the same fashion as a feeder structure. For an example of a switching frame arrangement refer to Figure 64 (a).

A typical switching frame consists of two vertical support columns located at each end of the structure and four horizontal members spanning between them. The upper two horizontal members provide attachment points for the switches. The lower set of horizontal members is located to suit the operating handles of the various switches. Figure 64 (b) is a photo of the switching frame arrangement shown in Figure 64 (a). At some locations access to the switch frame needs to be provided due to site conditions. An example of a switching frame with access can be seen in the photo provided in Figure 64 (c).



The number of switches required at a switching structure along with their spacing and component details are supplied by the electrical designer. These inputs define the switching structure geometrical requirements which are designed and documented by the civil design engineer.

All switching structures are to be designed in accordance with current Australian Standards and requirements documented in ESC 330. Loadings and load combinations shall be in accordance with AS/NZS 1170 and will consider dead, live and wind loadings. Structural steelwork shall be designed in accordance with AS 4100 and be galvanized in accordance with AS 4680. Concrete footings are to be designed in accordance with AS 3600 and AS 2159.

Consideration needs to be given to self weight and wind loading on all electrical equipment and cabling. Wind loading on cables can be adopted from Section 5.9.2.



(a) typical switching frame arrangement

(b) photo of typical switching frame

(c) switching frame with access provided

Figure 64 : Typical switching frames

All switching frames must provide an operator‘s platform consisting of steel mesh electrically connected (bonded) to switch operating handles for operator safety. For switching frames at ground level the mesh should be placed on 300 mm deep blue metal and secured in place by suitable means.

If access to the switch frame is required then requirements of AS 1657 need to be satisfied for components such as stairs, handrails, kick boards and flooring.

5.10 Electrical isolation

When overhead wiring structures are attached to reinforced concrete structures, e.g. retaining walls, overhead concourses and bridges, they have the potential to transfer



stray DC currents into the reinforcement that eventually leads to corrosion and damage to the structure. Also, overhead wiring structures located in public areas that come in contact with or that are within reach of other steel components, e.g. platform canopies and fences, can develop different electrical potentials which may cause an electric shock to anyone that touches both structures simultaneously.

To prevent these types of incidents from occurring, electrical isolation of certain overhead wiring structures needs to be implemented. Electrical isolation can take a number of different forms and ranges from simple separation of the two steel structures, to prevent them being touched at the same time, to providing insulation material between the overhead wiring attachment, e.g. drop vertical or bracket, and the structure, e.g. portal bridge or the concrete element.

Stray DC currents result from the traction system finding alternate paths back to the substation, e.g. through metallic pipes, steel reinforcement and the general mass of earth and can come from:

Overhead wiring, through leaky insulators; Rail, as rail potential is not earth potential.

5.10.1 Electrical isolation by separation

In public areas the best way to deal with electrical isolation of structures that have the ability to cause touch potential problems is during the placement of the structure. An overhead wiring structure should be located so there is 2.1m minimum clear separation between it and other steel objects. This is greater than the span of outstretched arms. This would include, but is not limited to, objects such as light poles, guards indicator posts, public telephones and ticketing machines.

Older types of platform and boundary fences commonly extend for long distances without a break and have the ability to pick up stray ground current that can cause a touch potential difference between them and an overhead wiring structure. Regular isolation gaps are required by current fence standards. On platforms where the overhead wiring structure can only be located next to a fence a break in the fence needs to be detailed to provide electrical isolation. The fence needs to be terminated 2.1 m either side of the structure, with a 4m isolation panel in between and 100 mm gaps to separate the panel from the rest of the fence. The fence posts of the isolation panel should be connected to footings or the platform concrete slab with electrically isolated anchors as described in Section 5.10.2.2. This provides a small length of fence within contact distance of the structure which is not likely to pick up stray ground currents.

Another large steel structure found on platforms that is capable of becoming a touch potential problem with overhead wiring structures is the platform canopy. If the canopy and the overhead wiring structure are separate structures the support columns need to have 2.1 m clear separation from an overhead wiring structure mast. In addition to this ground level separation, if the overhead wiring structure passes through the canopy roof a gap that provides at least 50 mm clearance to the metal roof sheeting needs to be provided. The infill used to prevent roof leakage needs to be made from a nonconductive material. Approval for the proposed material must be obtained from the Chief Engineer Electrical.

Overhead wiring fittings can be attached to reinforced concrete structures provided there is a guaranteed 50 mm separation between any reinforcing steel and metal attachment components. Only one approved product, the HILTI HIT-Bar does not need to met this requirement which is discussed in Section 5.10.2.2. A number of different ways to achieve this are available but require strict supervision during manufacture and installation. These methods are:



Casting of threaded ferrules into precast concrete girders during manufacture or at the insitu concrete pour during construction. Techniques used to hold the ferrules in place during the concrete pour must not be of a material that will provide an electric path to the reinforcement. A separation of 50 mm between the ferrules and the reinforcement also must be achieved. It is essential that adequate hold points and releases are present in the contract to ensure the required separation is achieved. On most projects this is not feasible and so this is not the preferred RailCorp method.

Clamping around a precast girder. As with the first method this requires design to be available during early stages of the structure‘s construction which is not always possible. The attachment fitting is clamped around the girder by bolts using the nominal gap between the girders to connect to a top plate. The top plate is encapsulated when the insitu deck is poured so positive anchorage is achieved. Strict supervision is required to ensure that deck reinforcement maintains 50 mm separation from the top plate and anchorage bolts.

Chemical or mechanical anchors. Drilled into precast or insitu concrete to place chemical or mechanical anchors is only an option if the exact location and depth of the reinforcement can be determined so 50 mm separation is achieved. This method should be limited to unreinforced concrete elements.

All solutions used to provide electrical isolation by separation need to be discussed with the electrical designer for the project and accepted by the Chief Engineer Electrical.

5.10.2 Electrical isolation using insulation material

When overhead wiring fittings are attached to reinforced concrete structures using chemical anchors and a guaranteed 50 mm clearance to the reinforcement cannot be achieved the support attachment needs to be provided with electrical isolation through the use of an insulation material at the point of connection to the structure.

When overhead wiring structures and platform canopies make use of the same structural steel components an insulation material must be used to prevent the transfer of stray currents into the canopy structure. On an overhead wiring structure that requires electrical isolation the best location to place the electrical isolation point is at the connection of the drop verticals to the bridge (assuming no mast registration is involved) as the loads the material needs to withstand are lower than for other options such as under mast base plates, better still is secondary insulation on the OHW cantilevers. (Closer to the source of the problem).

Currently two products are approved that provide electrical isolation when detailed and installed correctly. These products are:

Acetal copolymer (black); HILTI HIT-Bar, Which is the preferred method but does have some limitations,

Each of these products is discussed in the following sections.

5.10.2.1 Acetal copolymer (black)

Acetal copolymer (black) such as Sustarin C is approved by the Chief Engineer Electrical for use in providing electrical isolation to prevent DC stray current from passing from the overhead wiring system into a structure through the OHW fittings.

The purpose of the Sustarin C insulation material is to provide an insulation barrier between the overhead wiring attachment and the bolts or anchors fixing that are attached to the reinforced concrete structure or steelwork. If there is no direct contact between the anchor bolt and the steel fixing, stray current can not pass into the reinforcement or the steel structure.



To achieve electrical isolation two components made from Sustarin C, (described below) need to be detailed to suit the geometry and dimensions of the steelwork being attached to the structure. In addition the fitting being attached will also require some special detailing and steel components. A typical attachment showing an electrical isolation arrangement is shown in Figure 65.

(a) typical attachment to concrete

(b) detail of electrical isolation

Figure 65 : Typical electrical isolation arrangement using insulation material

A description of each component and their design and manufacture requirements follows:

Insulation pad: The first Sustarin C component is a 6 mm thick insulation pad that will sit between the fitting and the structure to which it is being attached. The pad size is determined by the contact area with the structure plus an allowance of 5 mm each side if the structure surface continues beyond the fitting. Attachment to the underside of a large concrete structure would require the insulation pad to be 5 mm larger on all sides of the fixing plate. Refer to Figure 66 (a) for typical details. When clamping to a steel member the additional 5 mm is only added in the direction that the steel member continues. The sides parallel with the steelwork direction are made flush with the fixing plate of the attachment. Refer to Figure 66 (b) for typical details. Holes are located in the pad to suit the attachment plate drilling and anchor bolts. The diameter of the holes is 10 mm larger than the anchor bolt diameter to allow for the insulation bush to fit between the bolt and insulation pad.

(a) large surface attachment

(b) structural beam attachment

Figure 66 : Typical sustarin C insulation pad details

Insulation bush: The second Sustarin C component is an insulation bush that fits over the anchorage bolts and prevents them from making contact with the attachment plate. At the top of the bush a wide collar prevents the special washer



and nuts from making contact with the attachment plate. Internal diameter of the bush throat s 2 mm greater than the anchor bolt diameter. The external diameter is 8mm greater than the anchor bolt diameter which produces a 3 mm thick isolation barrier around the anchor bolts. Depth below the underside of the top collar is the thickness of the attachment plate plus 4mm. When assembled the bush protrudes into the insulation pad by 4 mm preventing any contact between the anchor bolts and the attachment plate. Refer Figure 65 (b). The collar component of the bush is 4 mm thick and has a total diameter of 3.5 times the anchor bolt diameter. Figure 67 (a) shows a typical insulation bush giving manufacturing dimensions.

(a) insulation bush details and dimensions

b) special washer details and dimensions

Figure 67 : Typical insulation bush and special washer details

Special washer: A steel washer is specially made to transfer the nut force across the large hole in the attachment plate and prevent crushing of the insulation bush collar. Grade 250 steel 6 mm thick is used to fabricate the special washer which is 10 mm less in diameter than the total diameter of the insulation bush collar giving a 5 mm stop on the insulated collor. The inside diameter of the special washer is to be 2 mm larger than the anchor bolt diameter.

Attachment plate modifications: The attachment plate on the fitting being attached will require larger holes than normal due to the insulation bush. Holes 10 mm larger than the anchor bolt diameter are required to be detailed. If standard components are being specified, e.g. drop verticals, existing hole sizes need to be increased and edge distance checked.

All solutions used to provide electrical isolation by using insulation material need to be discussed with the electrical designer for the project and accepted by the Chief Engineer Electrical.

5.10.2.2 HILTI HIT-Bar

The HILTI HIT-Bar is a proprietary stainless steel threaded anchor rod that is installed with chemical adhesive and has been given approval by the Chief Engineer Electrical for use when electrical isolation is required. The embedded portion of the threaded anchor rod is precoated with epoxy that provides sufficient resistance to electrical current to allow the component to which it is attaching to be electrically isolated and not transfer any stray currents into the concrete structure through the anchor rod. Figure 68 shows the green epoxy coating on the HILTI HIT-Bar over the stainless steel threaded rod.



Figure 68 : HILTI HIT-Bar

To ensure that no surface contact occurs between the attachment steelwork and any steel or reinforcement embedded in the concrete structure a Sustarin C insulation pad is installed between the two contact surfaces. A typical arrangement showing an attachment using a HILTI HIT-Bar is shown in Figure 69 (a) and (b).

(a) typical attachment to concrete

(b) detail of electrical isolation

Figure 69 : Typical HILTI HIT-Bar arrangement

A description of each component used in the HILTI HIT-Bar arrangement and their design or manufacturing requirements follows:

Insulation pad: A 6mm thick Sustarin C insulation pad sits between the steel fitting and the concrete structure to which it is being attached. The pad size is determined by the contact area between the structure and the fitting plus an allowance of 5 mm on all sides. Holes are located in the pad to suit the attachment plate drilling and anchor bolts. The diameter of the holes is 2 mm larger than the anchor bolt diameter. Refer to Figure 70 for typical insulation pad details. If the electrical fitting extends beyond the concrete structure to which it is attached then the insulation pad will need to be terminated a minimum of 50 mm before the edge of the concrete. The pad should only continue beyond the centreline of the bolt for the same distance as it does in other directions on that fitting arrangement.



Figure 70 : Typical HILTI HIT-Bar insulation pad details

HILTI HIT-Bar: The HILTI HIT-Bar is installed in plain or reinforced concrete using HILTI HIT-RE 500 chemical adhesive as it has superior properties to other adhesives offered by HILTI. The HIT-Bar‘s insulation coating is susceptible to poor installation processes (e.g. poor hole cleaning and handling in a dirty environment). Twenty four hour curing time is required before installing the fitting and applying loading. A conservative design approach should be taken when calculating anchorages. Design for the anchors shall be in accordance with HILTI design procedures for HIT-RE 500 injection adhesive with standard threaded rod given in the Hilti Australian Fastening Technology Manual and the following recommendations given by RailCorp.

Anchor in tension:

To calculate the concrete cone/pull-out resistance (NoRd,c) the Mean Ultimate Load,

given in the HILTI HIT-Bar data sheet in Figure 5.61, is divided by a safety factor of 4 to obtain a safe working load. The safe working load is multiplied by a partial load factor of 1.4 to obtain No

Rd,c. This advice was given by HILTI in an email to RailCorp dated 10/11/04. Using a safety factor of 4 and a partial load factor of 1.4 brings the HILTI HIT-Bar capacity back to about what is given in the HILTI Fastening Technology Manual for a standard threaded rod.

Figure 71 : HILTI HIT-Bar technical data with HIT-RE 500

The Mean Ultimate loads given in Figure 71 have been determined in concrete with a cube compressive strength (fcc) equal to 30 N/mm2, which is equivalent to a cylinder compressive strength (f‘c) of 25 MPa. Values in the HILTI Fastening Technology Manual for a standard threaded rod are based on a cylinder compressive strength (f‘c) of 20 MPa. An No

Rd,c calculated for a HILTI HIT-Bar by the method described above is not to be increased by the influence of concrete strength factor (fBV) given in the HILTI Fastening Technology Manual for concrete strengths above 25 MPa. Calculated No

Rd,c values for a HILTI HIT-Bar need to be reduced by fBV = 0.95 when used in concrete of 20 MPa strength. The HILTI HIT-Bar should not be used in concrete that has a design compressive strength (f‘c) less than 20 MPa.



A comparison of concrete cone/pull-out resistance (NoRd,c) for both the HILTI HIT-

Bar and a standard threaded rod in 20 MPa concrete with HIT-RE 500 injection adhesive is given in Table 5.8.

Threaded rod size / anchorage depth

HILTI HIT-Bar NoRd,c (kN)

Standard threaded rod NoRd,c (kN)

M8 / 80 12.2 12.4 M10 / 90 17.8 16.6 M12 / 110 22.8 23.8 M16 / 125 34.0 34.7 M20 / 170 57.2 62.9

Table 10 : comparison of concrete cone/pull-out resistance

In advice to RailCorp HILTI recommend using spacing and edge distance reductions as per the HILTI Fastening Technology Manual. As these reductions are influenced by the hole diameter, and the HILTI HIT-Bar requires a larger diameter hole then a standard threaded rod, RailCorp recommend reductions for the next rod diameter size up be used with HILTI HIT-Bars (e.g. for M16 HILTI HIT-Bar use M20 reductions).

The steel design tensile resistance (NoRd,s) is obtained from the HILTI Fastening

Technology Manual for threaded rod of the appropriate size using HAS-R material designation as the HILTI HIT-Bar is manufactured from stainless steel (grade A4-70 or grade 316).

Anchor in shear:

To determine the concrete edge design resistance (VoRd,c) the values are taken

from the HILTI Fastening Technology Manual for the appropriate anchor size in standard threaded rod. RailCorp recommend that the value of Cmin (minimum edge distance) be increased to the next rod diameter size (e.g. for M16 HILTI HIT-Bar use M20 Cmin). Spacing and edge distance factors are calculated using this determined Cmin value.

The steel design shear resistance (VRd,s) is obtained from the HILTI Fastening Technology Manual for threaded rod of the appropriate size using HAS-R material designation as the HILTI HIT-Bar is manufactured from stainless steel (grade A4-70 or grade 316).

Combined action:

The anchor also needs to be checked for the combined action of tension and shear. This check shall be undertaken using the method given in the HILTI Fastening Technology Manual with values for tension and shear as determined using the method recommended by RailCorp.

Product availability and delivery lead time should be checked prior to specifying the use of a HILTI HIT-Bar to ensure supply will be available for the project.

6 Design of signal gantries

This section has been left intentionally blank as it will be added to the manual during a subsequent revision.



7 Assessment of existing structures

When an existing overhead wiring system is upgraded to a system with greater electrical capacity or an existing wiring system is modified, causing an increase in structure loading, the decision whether or not the existing overhead wiring structures can be reused is one of the major considerations for the project and needs to be addressed as part of the design process. Wire configuration changes that increase loadings on existing overhead wiring structures require a structural and condition assessment to be undertaken with favourable results for the structures before they can be reused.

7.1 Reuse of existing structures

The decision to reuse an existing overhead wiring structure needs to be made early in a project. Generally the type of overhead wiring changes proposed along with the age and condition of the overhead wiring structure will dictate if it is practical to make use of that structure in its current condition or whether modification, repairs, strengthening or replacement is required.

As modifications to overhead wiring are intended to enhance the life of the system the structures must also be able to provide support for the extended life of the overhead wiring. Existing structures that are reused must have a minimum of 25 years design life if the structure is greater than 25 years old or 50 year design life if the structure is less than 25 years old. In addition to confirming compliance with ESC 330 for strength and serviceability the project must design, document and carry out any repairs or strengthening required to achieve the required design life

Situations in which structures can often be reused are listed below and expanded upon in the proceeding sections where additional detail and some general recommendations are given.

Wire adjustments; Conversion to independent registration; Conversion from fixed wiring to regulated wiring; Modifications to existing regulated wiring; Upgrading of existing wiring system;

7.1.1 Wire adjustments

Wire adjustments are overhead wiring works based around making field adjustments to existing wiring to accommodate modified track alignment such as track regrading, turnout renewal, and track centre improvements. Usually wire adjustment works do not involve the addition of wire to the existing structures but if loadings on them are changed an assessment should be undertaken to determine if the structures are adequate.

In most cases wire adjustments do not have an effect on the structure loading or the load change is not significant enough to cause the existing structure to become overloaded. Deflection is usually the controlling factor especially if a loading imbalance is introduced to the structure when the wire adjustments are made.

Only structures that have a significant load increase or a significant change in the loading configuration need to have a structural analysis performed to check compliance with ESC 330 for both strength and serviceability. Existing structures should also be inspected for any signs of corrosion or defects that will affect their performance. Existing structures should be structurally assessed in the ―as is‖ condition.



7.1.2 Conversion to independent registration

To improve reliability of an existing fixed overhead wiring system the span wire and hanger arrangement, which provides support and lateral positioning of the wire, is replaced by drop verticals for each track making their attachment point independent.

With independent registration, the overhead wire loading will be applied to the drop vertical rather then through the hanger and span wire. All overhead wire loads are transferred to the bridge of the structure, resulting in vertical and horizontal loading creating greater moments in the masts. Out of plane moments on the bridge are also increased due to wind loading on the new drop verticals resulting in torsional loadings on the bridge causing out of plane deflection.

Structural assessment should be undertaken to ensure the conversion to independent registration does not cause the structure to become non compliant with ESC 330. The actual condition of the steelwork and footing need to be considered.

7.1.3 Conversion from fixed wiring to regulated wiring

Some overhead wiring projects involve converting a fixed wiring system to a regulated system using the existing structures. It is this type of project where reuse of existing structure becomes very difficult to achieve due to the loading differences between the wiring systems involved.

Regulated loadings are normally larger than fixed loadings due to the greater amount of copper in the system configuration required to deliver the electrical capacity. As a result higher tensions in the conductors are required to reduce the effect of this weight on sag. The higher the tension load the greater the radial loads. The combination of higher weight and radial loads may be up to 30% greater than fixed loadings requiring the overhead wiring structures for regulated systems to be generally of slightly heavier section when compared with existing.

A large proportion of the weight and radial loading is transferred to the bridge of the structure through the drop vertical resulting in not only vertical and horizontal loading increase but also, in the case of temperature variations or if twin drop verticals are used, torsional loading on the bridge. Most structures designed for fixed systems use open sections that have low torsional capacity that become unsuitable in overlap structures where twin drop verticals are required and for structures where large longitudinal wire movements are experienced.

The reuse of existing structures in this type of project is usually limited to structures that are less than 25 years old and in good condition. All existing structures that fit in this category will require rigorous analysis to ensure compliance with ESC 330. Existing structures that are not galvanized and are in poor condition should be replaced.

7.1.4 Modifications to existing regulated wiring

Some overhead wiring projects involve undertaking modification to the existing regulated wiring to provide better electrical performance. The most common modification is to convert a single run of wiring, one end being fixed and the other moving, into two tension lengths by the addition of a fixed mid-point. The single length of wire is anchored at a structure located midway along its length and tensioned from both ends.

Only a small number of structures in each existing run of wire are affected by a change in loading. The structure that supported the fixed end is converted into a moving end by the addition of weights. Tension and radial loads remain unchanged but additional axial load and moments are applied to the structure due to the addition of weight stacks. The increase in loading is not usually a problem because the structure has a guy rod that



provides out of plane load restraint. At the newly constructed fixed mid-point one or more existing structures will require the attachment of an anchor or the clamping of the fixed mid-point to the bridge. Guy rods and guy footings are usually added at these structures to help with out of plane loads generated by tension imbalance or wire breakage.

Another modification to an existing regulated system is the addition of an auxiliary feeder. The auxiliary feeder is usually supported from the existing structures and will increase the weight and radial loads on the structures that it is attached to. Due to the increased loadings the structures will need to be checked, for strength and serviceability, to determine if they are capable of carrying the increased loading.

7.1.5 Upgrading of existing wiring system

When the project involves a rebuild that replaces the existing overhead wiring system with a similar one that produces no additional loading and does not change the way it is configured then the existing structures are deemed to be satisfactory provided they are galvanized and in good condition. Old structures that are not galvanized should generally be replaced as part of the upgrade works.

If the wire upgrade involves increasing the electrical capacity a heavier wire system is usually used to replace the existing. An increase in the wire system size will result in more weight load and higher tension which translates to increased radial loadings.

7.2 Load reduction on existing structures

When undertaking the analysis of existing overhead wiring structures there is only a small amount of scope for reducing loads as structures must be loaded and analyzed to current Australian Standards. Some areas exist within the control of RailCorp where loadings can be reduced or refinement to RailCorp requirements made. These areas are:

Wind Loading reduction; Live load (construction requirement) reduction; Longitudinal wire movement reductions;

The following sections discuss how these reduced loadings are derived and under what conditions they can be applied. The discussions are based around the load cases, modelling and design methods discussed in Section 5.

7.2.1 Wind loading reduction

If an existing overhead wiring structure is 25 years or older then in accordance with Section 5.4.2.4 Table 3 the design working life can be reduced to 25 years which in turn will reduce the probability of exceedance and the design wind speed. A typical reduction in design wind speed decreases the wind pressure by about 12% when calculating strength limit state loads. This reduction can be applied to both the structure loads and the wire loads and will affect Load Cases LC4, LC5, LC6 and LC7.

These wind load reductions will help when determining the strength limit state compliance but do not apply to serviceability limit state as the serviceability wind design speed is not determined by design life and age of the structure but by a probability of exceedance specified in ESC 330. To enable existing structures to comply with serviceability requirements and be reused the acceptance criteria for serviceability deflections has been relaxed for some components. Refer to section 7.3.2 for increased acceptance limits for existing structures.

If the strength limit state wind load has been reduced due to the structure being older than 25 years a new reduction ratio for the amount the strength limit state wind load is multiplied by to obtain serviceability limit state wind load will need to be used. Load Case



LC 14, LC 15, LC16 and LC 17 will need to have Primary Load Cases LC 4, LC 5, LC6 and LC7 modified by multiplying each by a value of 0.73 instead of 0.65.

Further reductions in the wind loading may be able to be applied to an existing structure at a specific location. The wind loads given in this manual are based on a wind direction multiplier (Md) equal to 1. If the orientation of the structure is known a lower value may be able to be applied for the direction that is causing non compliance. No shielding of structures has been considered in wind loadings used which may be applicable to the structure under analysis and should be investigated if additional load reductions are required.

7.2.2 Live load reduction

For the design of new structures Load Case 2 requires a live load of 1.07 kN to be applied at each wire attachment point on a structure. This load should be applied to existing structures in the first instance but if it is found that this loading is causing the existing structure to fail in strength limit state it should be progressively removed from each attachment point to find out if the structure can sustain any live loading.

If a reduction or complete removal of live loading is required to allow an existing structure to be reused then RailCorp approval is required before the structure can be accepted for reuse. Approval from both the Civil and Electrical Maintenance Engineers will be required as well as acceptance from the Chief Engineer Civil.

The live load case is used to simulate occasions when construction or maintenance staff may be required to carry out works from a ladder against the conductors or standing on the contact wire. As nearly all construction and maintenance activities are undertaken using mechanical lift devices and the OH&S requirements almost preclude this type of work activity it should not be difficult to get approval to restrict live load from structures. The biggest problem becomes how to control or ban live loading of the particular structures. In consultation with Maintenance Engineers a strategy to control live loading on the affected structures should be implemented. Some suggested controls are:

Work method statements; Restricting live load from an area; Signage on affected structures;

If live load is the controlling factor in the reuse of an existing structure then the removal of this type of loading from the structure should be pursued.

The effects of live load on the existing structure can be further reduced by considering the actual longitudinal wire movement when determining the out of plane loading. Determination of longitudinal wire movement is discussed in Section 7.2.3 but the reduction calculated for live loading must consider the ultimate temperature range as live loading is only considered as a strength limit state case.

7.2.3 Longitudinal wire movement

When designing new overhead wiring structures a blanket value of 500 mm longitudinal wire movement (i.e. in the direction of the track) is applied to all structures when calculating the out of plane forces generated due to wire weight load and live load. This value is adopted as it represents the maximum swing that the electrical fittings can achieve on an OHW Cantilever and is also the limit placed on wire expansion by Electrical Design Standards. This approach is satisfactory for new structures but often causes excessive out of plane loadings when an existing structure is being analysed to determine if it is suitable for reuse with a new wire system or altered existing configuration.



If an existing overhead wiring structure is being analysed, to determine if it is suitable for reuse under new loading conditions, and fails in strength or serviceability using 500 mm longitudinal wire movement then the amount of movement needs to be reduced to an appropriate calculated actual movement. The actual amount of movement will be different depending on which limit state is being investigated.

To calculate the longitudinal wire movements at a location three inputs are multiplied to obtain the amount of wire movement. These are:

Distance the structure is located from the fixed end or fixed mid point of the wire run. This value, in metres (m), is obtained from the Electrical Layout by determining the difference between the structure location number of the fixed point of the wire and the location under investigation. (If location numbers are accurate).

The coefficient of expansion which for copper is 17x10-6/oC. Change in temperature from the neutral position of the wire (+ or -) in oC. The

neutral temperature is subtracted from the minimum and maximum wire temperatures with the greatest value used to calculate a movement value. The direction of the wire movement at each attachment on the structure must also be considered, especially when twin drop verticals are being used, as the wires could be moving in opposite directions due to fixed and moving ends being located on different sides of the structure. Advice on determination of temperature ranges for the different limit states is given below and obtained from Electrical Design Standards.

For strength limit state calculations the longitudinal wire movement at a particular location shall be calculated using the minimum and maximum ultimate temperature range defined by the power study or design criteria.

For serviceability limit state calculations the longitudinal wire movement at a particular location shall be calculated using serviceability temperature ranges. This should represent a service range of temperature that the structure would experience during an average daily load cycle.

The minimum serviceability temperature is determined using the average daily minimum temperature experienced within the Sydney electrified area obtained from the Bureau of Meteorology. The values in Table 11 are proposed but should be confirmed by the design engineer for the particular project or structure being analysed.

Geographical Area Defined by locations Minimum Temperature

Sydney Newcastle, Emu Plains, Macarthur and Kiama

6oC

Blue Mountains Emu Plains to Lithgow 3oC

Table 11 : Average daily minimum temperature

The maximum serviceability temperature is determined by the addition of three inputs:

The average daily maximum temperature experienced within the Sydney electrified area obtained from the Bureau of Meteorology. The values in Table 12 are proposed but should be confirmed by the design engineer for the particular project or structure being analysed; plus

Geographical Area Defined by locations Maximum Temperature

Sydney Newcastle, Emu Plains, Macarthur and Kiama

30oC

Blue Mountains Emu Plains to Lithgow 27oC

Table 12 : Average daily maximum temperature



Solar radiation effects on the wire which are dependent on geographical location, conductor size and other factors such as wind effects. This input value is determined at individual locations or for the project in consultation with an up to date Power Study and input from an electrical design engineer. A value in the range of 4oC to 6oC is suggested but needs to be confirmed for the particular project or structure being analysed; plus

Wire temperature increase due to current contribution also needs to be considered. A value for this component is very dependent on the location of the structure in relation to the feeding point, overhead wiring system in use, timetabled usage and rolling stock type. The most recent Power Study for the area under consideration should be analysed by an electrical design engineer to determine a suitable value. A value in the range of 7oC to 10oC is suggested but needs to be confirmed for the particular project or structure being analysed.

A demonstration of the possible movement differences that can be gained by the implementation of this method is setout in the Example.

Example:

A structure positioned 425 m from a fixed mid point located in the Sydney geographical area would have the following design movements applied:

If a new structure a 500 mm longitudinal wire movement would be applied to both strength and serviceability limit state load cases.

If an existing structure the strength limit state design longitudinal wire movement would be:-

Design temperature range from standard or power study = 0oC to 67oC.

Neutral temperature = 21oC. (May be 25 oC for future work)

Min & max design temperature ranges = -21oC and 46oC.

Cold Longitudinal movement = 425x17x10-6x-21 = -151 mm towards fixed end.

Hot Longitudinal movement = 425x17x10-6x46 = 332 mm away from fixed end.

Design would be based on the larger of the two wire movements or the combination of wire movements that produces the worst design effects.

If an existing structure the serviceability, (maximum allowed daily movement) limit state design longitudinal wire movement would be:

Design temperature range

Min temperature = 6oC. (Table 11)

Max temperature = 30oC (Table 12) + 4oC + 7oC = 41oC.

Neutral temperature = 21oC.

Min & max design temperature ranges- = -15oC and 20oC.

Cold Longitudinal movement = 425x17x10-6x-15 = -108 mm towards fixed end.

Hot Longitudinal movement = 425x17x10-6x20 = 146 mm away from fixed end.



Serviceability check would be based on the larger of the two wire movements or the combination of wire movements that produces the worst deflections.

Reduced longitudinal wire movements affect both the weight load (LC1) and the live load (LC2). Reductions to out of plane movements should be applied to the existing structure model to refine the loading applied.

7.3 Acceptance limit reduction

When undertaking the structural assessment of an existing structure to determine if it is suitable for reuse it will often fail the acceptance requirements when compared with new structure requirements.

Two areas of acceptances are:

Strength limit state Serviceability limit state

7.3.1 Strength limit state

No reduction in the Australian Standards acceptance criteria for strength limit state can be given to existing structures that are being assessed for reuse under new loadings. An opportunity exists for the design engineer to refine some of the loads that are applied to the structures by using specific site values for wind loading and longitudinal wire movements. These combined with the reduction given in design life for structures over 25 years may allow modern (e.g. UC sections) existing structures to comply with strength limit state requirements.

7.3.2 Serviceability limit state

Acceptance of existing structures for compliance with serviceability limit state is often the hardest to achieve as the requirements for new structures are very stringent as they are orientated towards providing structures that are robust and display very little deformation.

To allow existing structures to be utilized a number of refinements to the loads have been described in the previous sections. Even with all of these refinements applied the existing structures may not comply with the limits allocated for new structures.

To maximise use of existing structures that comply with strength limit state requirements a relaxation in some of the deflection limits has been determined. Deflection of an existing overhead wiring structure under static serviceability loading – permanent actions only, no wind or live load – shall be limited so aesthetic appearance of the structure is acceptable. Deflection limits in Table 13 should be achieved as a minimum to provide the serviceability limits for acceptance of existing structures.

Structure or Component Type

Maximum Vertical Deflection

Maximum Horizontal Deflection (In and Out of Plane)

Portals Span / 250 Height / 75 Single Mast N/A Height / 75 Cantilever Length / 75 (+ve)

Length / 300 (-ve) Height / 75

Drop Verticals N/A Length / 35

Table 13 : Existing structures static deflection limits

These limits are applied to the final deflected shape, which must take into account any mast rake on cantilever structures and bridge or boom camber on portals and cantilever structures.



Lateral deflection of the contact wire attached to an overhead wiring structure shall be limited to 50 mm, with only serviceability condition wind loading (no radial or other loads applied).

7.4 Typical existing structure

There are some configurations of existing overhead wire structures that have inherent problems when the wire configuration is altered. If these structures have protective coating and are in very good condition they should be given every chance to be reused. The following sections look at each and describe where they fail and what can be done to make their reuse a reality.

7.4.1 Universal column portal structures

Portal structures with masts and bridges fabricated from 250 UC 73 and 310 UC 97 section have been used extensively since 1975. Structures using these sections were used to span up to four tracks. The first versions of portals using these sections were detailed with the bridge connection on top of the mast which does not provide any restraint to the top flange. The base plate connection to the footings consisted of two bolts and a ―rocker plate‖ forming a pinned connection in plane. A pinned base connection allows a shallow footing to be used. Drawings E1-102 and E1-103 document these structure types.

In 1989 the drawings were superseded by drawing E1-192 and E1-193 where the major modification was the mast/bridge connection. A cleat arrangement on the top and bottom flange of the bridge moved the mast/bridge connection to a location 500 mm below the top of the mast providing top flange restraint.

Further improvements were made in 1993 when these structures were superseded by drawings E0-409 and E0-428. The mast/bridge connection remained attached using a cleat but a six bolt base plate was introduced creating a fixed mast base. As a result the footing size was increased and a pile type footing option was included to resist the greater moments now produced at the base of the structure.

All configurations of these types of structure struggle to provide adequate out of plane serviceability deflections when large wire movements of regulated systems are transferred via drop verticals. The majority of the deflection is due to the poor torsional capacity of the bridge universal column section. When altering the conductor configuration some arrangements that will cause increased deflection are:

The addition of another set of conductor wires to an existing single drop vertical using a back to back arrangement, if the longitudinal wires movements are in the same direction. (I.e. both moving ends are on the same side of the structure location.)

Adding more single drop verticals with sets of conductors to the structure will also cause excessive out of place deflections if wire longitudinal movements are in the same direction as the existing wires.

Replacing a single drop vertical with a twin drop vertical or adding a new twin drop vertical to a UC portal will only work if the weight loads of both attachments are approximately equal to avoid out of balance loading. The longitudinal wire movements of the two wires will also need to be equal but in opposite direction.

Making configuration changes that increase radial loading on the structure or creates an out of balance loading on a twin drop vertical.

To make existing UC portal structures comply with the acceptance requirements when wire configurations are changed, the design engineer must use all load reductions available in Section 7.2 and the reduced acceptance criteria in Section 7.3 to give the



structures every chance of working. If the structure still fails to comply other options need to be investigated, they are:

Change the wire configuration to reduce the amount of out of plane loading being applied to the bridge via the drop vertical.

Make modifications to the existing structure. The most obvious is to replace the UC bridges with an appropriate SHS section. Direct replacement of a 310UC bridge with a 300 SHS may not be the best solution as these sections have long procurement lead time. A 250 SHS will be a more cost effective solution but will require special end plate details to match the existing bridge connection drilling.

Reduce the loading on the existing structure by adding the simplest type of new structure such as a single mast or cantilever mast.

All efforts need to be made to make use of existing structures that still have good protective coating and free from structural defects.

7.4.2 Cantilevered Structures

Cantilever structures with masts fabricated from SHS sections and booms consisting of UC or SHS section have been used extensively through the RailCorp system. Early cantilevers were constructed using drawing similar to E0-404 and consisted of 250SHS mast with a 200 UC boom. This configuration was replaced by drawing E1-158 which provided a 250 SHS boom making it a more satisfactory structure for use with out of plane loadings. Further developments have resulted in a 300 SHS cantilever mast and a 300 SHS light cantilever mast both with mast and booms fabricated from SHS sections.

Cantilever structures that have a UC section as the boom will not satisfy the design acceptance criteria for reuse in a regulated wiring system. These structures have been used extensively in the Blue Mountains to create independent registration but the overhead wiring system is fixed and produces no out of plane loading. If these structures have been used in a regulated situation that requires adjustment then the structure will most likely fail the acceptance requirements for serviceability. In these situations the option of replacing the boom with a SHS section will need to be investigated.

Special care needs to be taken when changing the wire and load configuration on an existing cantilever mast even when both mast and boom are fabricated from SHS. All of the methods to reduce the effects of loading on the structure that were discussed in Section 7.2 will need to be apply to any cantilever but the serviceability deflection limits are stricter than for a portal and need to be given special attention. To achieve the strict deflection limits consideration must be given to the effects of mast rake and boom camber that have been applied to the existing structure.

7.4.3 Parallel flange channel structures

Large span structures in the past have been constructed from two smaller sections of either PFC or UB which are placed parallel and spaced apart using battens and diaphragms to form a larger capacity section. These structures are painted or galvanized and when being assessed for reuse usually prove to be adequate for both strength and servicability.

Out of plane deflection of the drop vertical due to twisting of the bridge will be minimized as the bridges are heavily battened and have regular diaphragms that provide an almost box like structure. When modelling the structure it is important to ensure a representative value for the bridge torsion is used. If the torsional values for the two PFC or UB are only added then the resultant out of plane drop vertical deflection will be excessive. In many of the commercially available analysis software packages built up sections of this type can be generated but care should be taken as no allowance for the battens and diaphragms



is made by the software when calculating torsional properties. Consideration of the torsional stiffness provided by the battens and diaphragms must be applied to the model.

When checking the vertical deflection of the bridge consideration to camber that has been applied during fabrication needs to be taken into account. All PFC and UC portals over 12m in length have had camber applied to the bridge during fabrication.

7.4.4 Rolled steel joint and broad flange beam structures

Before UC, UC, SHS and PFC sections became available and standard structures were developed using the modern rolled sections OHWS portals were fabricated using a range of RSJ and BFB sections. These structures are still to be found within the Railcorp system, mainly in stabling yards and sections of OHW that have not been regulated such as the Blue Mountains.

It is difficult to make these types of structures comply with the acceptance criteria currently specified as the loading requirements have increased over the years along with the more rigorous code design requirements. Compliance becomes practically difficult when the structure is required to support regulated overhead wiring.

The condition of these structures becomes very important as they only had paint as a protective coating system which has most likely not been maintained or reapplied over the years. Section loss in these structures is quite common due to lack of protective coating.

Often even with all the local reductions applied and the reduced acceptance criteria applied reuse of these structures can not be achieved. A replacement structure to reduce loading or completely replace the existing structure may be the only solution.

7.4.5 Other structure configuration

A number of other structure configurations exist in the system that may require structural assessment at some stage. Many of these structures consist of Tapered Flange Channels (TFC) that have been fabricated into stronger structures through the use of plate battens. The masts are usually tapered providing a section with more capacity at the base. When a portal was required a bridge of similar construction was installed between the masts.

Some typical examples of these types of structures are the 32T Mast or 42CBN Bridge. Typical examples of these types of masts and bridges can be found in drawings D769 and B847 respectively.

As would be expected these structures have better structural capacity than the RSJ or BFB structures but will require load reductions as specified in Section 7.2 and reduced acceptance criteria as given in Section 7.3 to enable them to comply when an altered or new load configuration is proposed.

The problem that exists with these older fabricated structures is that very little is known about the condition of the protective coating that has been applied to the steelwork. Depending on the age of the structure it may have corrosion resulting in section loss. When assessing the capacity of these structures consideration needs to be given to the section loss along with future losses over the design life of the structure.

7.5 Condition of existing structure

An important aspect that needs to be investigated when an existing structure is being considered for reuse is its current condition. In accordance with TMC 110 Structures Service Schedules overhead wiring structures should have a detailed examination every



four years and a briefer mid-cycle examination resulting in an inspection of some type every two years.

The latest inspection report for the structure should be obtained from the asset owner to establish the current condition of the structure and determine if any reduction in cross section is required when determining the section and member capacity. If the inspection report is out of date, more than four years old, or it is obvious that further structure degeneration has occurred since the last inspection the design engineer should arrange for a new structure inspection to be undertaken.

When a structure inspection is required to be undertaken as part of the scope of a project the inspection shall be carried out as a detailed examination in accordance with TMC 110 service schedule SSC 220 and include the following tasks:

Supply of any labor and equipment required to clear vegetation and ballast to allow access to and inspection of the structure. The inspection of each structure is to be a visual appraisal with non-destructive measurement and testing only;

Supply professional services to carry out a detailed examination of each structure in the defined area in accordance with Service Schedule 220, ―Detailed Examination of OHWS and Signal Gantries‖, found in RailCorp Engineering Manual – Structures TMC 110 with the following amendments to tasks to be undertaken;

a) Tasks 1 to 8 inclusive are to be undertaken as documented;

b) Task 9 is not required to be undertaken but the engineer undertaking the inspection shall notify the Structures Manager or Civil Maintenance Engineer immediately if any defects found are considered to be an exceedence. Refer to RailCorp Engineering Standard – Structures ESC 302 Structures Defect Limits.

c) Tasks 10 to 12 inclusive are not required to be undertaken but are replaced by the structure condition report that is produced for the project.

One of the most critical elements that need to be recorded during a structure inspection is the amount of section loss, its location and the extent over which it occurs. Using this information the design engineer can calculate new section properties that are used in determining the ―As Is‖ structural capacity of the section or member under investigation.

If the structure has section loss due to corrosion but has been found to have adequate strength in the ―As Is‖ condition and it is intended to make use of the structure for a further 25 or 50 year design life, depending on the age of the structure, the design engineer needs to estimate additional section loss over the required design life. Atmospheric corrosivity zone and rate of corrosion for steel within that zone shall be determined in accordance with AS 4312 ―Atmospheric corrosivity zone in Australia‖ and capacity checked with the estimated section loss for the required design life.

8 Documentation requirements

8.1 Documentation types

The final design process for an overhead wiring structure is the documentation of the structure so it can be fabricated, erected and maintained in accordance with the design. Design intent is conveyed by drawings and technical specifications. The main purpose of this Chapter is to provide guidance on the type and level of detail to be provided on drawings prepared for documentation of the overhead wiring structure design.



In documenting overhead wiring structures there are three distinct types of drawings prepared. Each type of drawing has a specific purpose and requires the design engineer to provide the required information at each structure. The three drawing types are:

Structure diagram drawings: which are required for every project; Standard OHWS drawings; Location specific detail drawings; Documenting modifications to existing OHWS;

The content of each of these drawings, how they relate and are referenced to each other is explained in the following sections.

8.2 Structure diagram drawings

Overhead wiring structures are documented by producing a Structure Diagram for each location where a new structure is being provided or where modifications to an existing structure are being undertaken.

The Structure Diagram is very important as it is the structural design product and conveys the design intent to the construction phase of the project. It is also the permanent record of the infrastructure and is used for asset management, planning and maintenance activities.

The majority of Structure Diagrams Drawings use a scale of 1:100 that provides sufficient size to allow the relevant information to be included on the drawings. The Structure Diagrams shall be drawn as a cross section viewed with back to Sydney starting with the first structure being placed at the bottom left hand of the drawing sheet and continue placing subsequent structures in kilometrage from Sydney above the first structure. A second and third column, if sufficient room is available, of Structure Diagrams are placed to the right of the first following the same convention for placement. Refer to Appendix 2 for samples of typical Structure Diagrams.

A1 size drawing sheets should be used unless the number of structures involved in the project can be accommodated on a smaller single sheet. A3 size drawing sheets should only be used for single structure projects. Text should be 3.5mm in height for all notes and information placed on the drawing with the exception of headings and labels which should be 5mm in height. All drafting shall be undertaken to comply with the requirements of RailCorp CAD Drafting Manual. Drawings shall be submitted in a format that does not require colour printing to obtain the design intent or drawing clarity.

A Structure Diagram consists of a number of elements that combine to provide a unique set of information that describes the structure required. Each Structure Diagram drawing shall include the following elements, where applicable:

Structure number; Structure type and size; Horizontal location of mast; Vertical location of footing pedestal; Bridge/boom length; Mast height; Track centres and track names; HTRL; Drop vertical length, type and position; Footings; Features adjacent to the structure; Anchor heights; Anchor plate notation; Guy footings;



Bridge splice; Access prevention grille; Notes; References; PP/HP2 tables; Title Block; Special details; Special detailing referencing multiple standard structures; Multiple span portals;

If a particular element is not relevant to the structure location being documented then the information is simply omitted from the Structure Diagram. It is the design engineer‘s responsibility to ensure that all relevant information is provided and documented in accordance with this manual. The type of information that is required and how it is determined for each element above is now described in detail.

8.2.1 Structure number

Each OHWS is given a unique number/name so it can be described on electrical layout drawings and located in the field. The structure number is determined by Electrical Design and is an alphanumeric that provides a unique name for each structure location. The alpha component is a single or double letter that is assigned to each line or section of line where the structures are being used. The numeric component of the name is based on the approximate distance from the Sydney end of the suburban electric platforms at Central.

As track kilometrage is based on a different reference point the structure number does not usually correspond with the track kilometrage at that location. The structure number is used purely for identification purposes. For new structures it is not to be used for locating the structure along the track or setout of footings. On some major upgrading projects where every structure is being replaced some Regions have requested the number assigned to the structure be aligned with the track kilometrage. An issue of this nature is between the Region and Electrical Design and usually resolved before the structural design commences.

It is the design engineer‘s responsibility to ensure the structure number used on each Structure Diagram corresponds with the Electrical Layout. On the Structure Diagram the structure number is placed below and at the middle of the location cross section using a text height of 5mm. To highlight the structure number it is underlined. An example of a structure number is MH10+715 or H24+498 which can be seen in use in typical Structure Diagrams in Figure 8.1 to Figure 8.4.

On some old electrical layout plans and Structure Diagrams the structure numbers are in an older format that may need to be converted to the current system when searching for information on existing structure.

8.2.2 Structure type and size

Type and size of the OHWS required for a particular location is determined by the design engineer during the analysis and design component of the detail design. This information is documented on the Structure Diagram by placing a diagram of the chosen structure on the cross section and labeling it correctly.

The diagram of the chosen structure consists only of the outline of the steelwork and the mast centreline. Hidden line detail and flange thickness lines of rolled sections are omitted for clarity. The size of a particular type of standard structure chosen is nominated by placing a label on the diagram. Only the name of the structure designated in the standard drawing tile block is required to be placed on the Structure Diagram. E.g. 250



SHS Cantilever Mast or 250 SHS Portal. Nominating the section type and size for each component on the structure is not required. Only the Free Standing Anchor Mast standard structure drawing requires the designer to nominate a section size.

In portal and cantilever structures, the label is located above the bridge on portal structures and above the boom on cantilever mast structures. An example structure type and size nomination for portals and cantilevers is shown in Figure 8.1 and Figure 8.2.

Mast only structures such as PP‘s, HP‘s and FSAM should be labelled horizontally at the centreline above the top of the mast. An example of structure type and size nomination for mast only structure can be found in Figure 8.3 and Figure 8.4.

8.2.3 Horizontal location of mast

It is the design engineer‘s responsibility to ensure that all OHWS masts are located horizontally to comply with the requirements of RailCorp Transit Space Standard ESC 215. Clause 7.1.1 and Table 1 provide the requirements for mast adjacent to main line tracks while Clause 7.1.2 and Table 2 deal with mast adjacent to sidings. The dimensions in these tables are minimum infrastructure service requirements and should be provided where possible.

For masts adjacent to main line tracks ESC 215 requires a minimum clearance of 3000 mm from the face of the mast to the design centreline of track. When locating an OHWS mast the centreline is usually placed at 3200 mm from the design track centreline. This provides a 200 mm space to accommodate half the structure width.

Masts adjacent to sidings require minimum 2500 mm clearance in accordance with ESC 215. Similarly to main line the mast is located 200 mm beyond the clearance to allow for structure width giving a horizontal setout distance of 2700 mm.

When locating a mast the design engineer must ensure that it does not obstruct or clash with any existing rail infrastructure. Service search information should be used to determine the location of any service in the vicinity of the proposed mast location. Following are some typical rail infrastructure that needs to be considered when placing a mast:

Cess drainage and natural water courses; Pipe and sump drainage below ground; Signal cables and equipment both above and below ground; Communication cables; High voltage services both above and below ground; Drivers‘ view of signals (signal sighting);

If the mast needs to be placed at a distance greater than 3200mm to avoid existing rail infrastructure, then it can be moved out to about 3900mm before a drop vertical (mounted on the bridge or boom) will be required to support the wiring. Regardless of the distance the mast is moved the electrical designer will need to be notified so the electrical arrangement can be amended or a drop vertical added to the structure.

The horizontal location of an OHWS mast is documented on the Structure Diagram by providing the following information:

Track centreline offset: the distance from the centreline of the mast to the centreline of the nearest design track is shown. If the structure is located between two tracks than both distances need to be provided;

Survey coordinates: easting and northing coordinates are given that locate the centre of the mast section in plan view. The coordinates are usually provided in Integrated Survey Grid (ISG) but currently a conversion to Map Grid Australia (MGA) is in progress and more projects will start to use this coordinate system;



Structure orientation: for structures that consist of two or more masts, the orientation of the structure is defined and no further information is required. For single mast structure it is assumed that the mast is placed perpendicular to the design centreline of the track. To facilitate the structure setting out, a bearing giving the in-plane direction of the structure is provided. If the orientation of the structure is not perpendicular, as may be in the case of some FSAM, than a plan view indicating the required orientation must be provided;

Refer to Figure 8.1 to Figure 8.4 to see how the above information is applied to typical types of Structure Diagrams.

If the minimum infrastructure service requirement cannot be provided, then the mast is to be placed in a position as far as possible from centreline of track and checked for clearance from the General Kinematic Structure Gauge as defined by ESC 215 Clause 8.2. Structure clearances that do not infringe the General Kinematic Structure Gauge, but do not comply with the minimum infrastructure service requirement, will require approval by the Region before the drawing is issued for construction. If the mast can only be located in a position that infringes the General Kinematic Structure Gauge, then a Transit Space Waiver approved by the Chief Engineer Track in accordance with ESC 215 Clause 8.4 is required before the drawing is released for construction.

For a mast between two tracks where the minimum infrastructure service requirement cannot be achieved, the location is to be determined so the same clearance to the General Kinematic Structure Gauge is achieved, on both sides. Approval and waivers are required as for masts described above.

Masts that are used for moving anchors must have their weights and associated attachments considered in clearance calculations. The pedestal also needs to meet these clearance requirements if it is above the design rail level projected line including superelevation.

8.2.4 Vertical location of footing pedestal

The vertical location of the top of the pedestal is important and needs to be given due consideration. Each mast location will need to be considered individually and the most suitable height determined after consideration of all the factors influencing the decision. The following are factors to consider when determining the top of the pedestal:

The top of the pedestal should always be positioned so ballast or soil will not come in contact with the base plate or hold down bolts. An allowance needs to be made for future works including track re-grading and access road upgrade;

If the mast is located 3200mm from the design track centerline, the top of the pedestal should be between 200mm and 250mm below design rail level of the adjacent track. At this height ballast with the correct profile will not build up on the base plate and hold down bolts;

If the mast needs to be located closer to the track than the desired 3200mm, the top of the pedestal should be raised to account for the ballast height. The top of the pedestal should not normally rise above the design rail level of the track adjacent the mast;

If the mast is to be located further from the track than the desired 3200mm, the top of the pedestal should be lowered as the ballast profile will not present a problem. The top of the pedestal should remain at least 100mm above the natural ground line;

When a pedestal is located between tracks with tight centres the top of the pedestal should be placed at design rail level of the lowest track;

Pedestal heights for both masts of a portal structure should be kept at the same level provided all of the other listed considerations can be achieved;



In curved track locations the higher and wider ballast shoulder needs to be considered when placing the pedestal;

On the Structure Diagram the vertical location of the pedestal is nominated by providing a reduced level (RL) to which the top of the pedestal shall be constructed. The RL provided should be to Australian Height Datum (AHD) and be placed on the Structure Diagram adjacent to the footing above the setout coordinates as shown on the typical Structure Diagrams provided in Figure 72 to Figure 75.

8.2.5 Bridge/boom length

When documenting portal and cantilever mast structures, a bridge or boom length must be specified on the Structure Diagram. The bridge or boom length is shown using dimension lines, with the dimension noted as ‗L = (required length in mm) ‗. The value of the length provided on the Structure Diagram is used as an input on the standard steelwork drawing which is used to fabricate the structure.

For a portal structure the bridge length is the distance between the centrelines of the masts which support that bridge. This length is calculated by adding all track centres and mast offsets between the two masts. The L dimension is rounded up to the nearest 100mm wherever possible. This is normally achieved by adjusting a mast offset value to suit. The length is also checked by determining the distance between the setting out coordinates nominated for the two footings. A typical example of how a portal bridge length is specified can be found in Figure 72.

The boom length of a cantilever mast is defined as the distance between the centreline of the mast and the end of the boom. The boom length needs to be of sufficient length to accommodate the drop vertical end plate and stop bar. The ‗L =‘ value on the Structure Diagram is calculated by adding 550 mm to the drop vertical position dimension and rounding the result to the nearest 100mm. A typical example of how a cantilever mast boom length is specified can be found in Figure 73.

8.2.6 Mast height

Typically, an overhead wiring structure is constructed at a height of 7.5 metres above the rail level of the highest track which it is registering. This height provides sufficient attachment points for most overhead wiring systems used. If a structure of greater or lower height is required then the special requirement will be determined by Electrical Design and noted on the Electrical Loading Diagram.

The mast height documented on a Structure Diagram is the H, HL or HR value required by the standard drawing for fabrication. The determination of this value differs depending on the type of structure being documented. The different height determinations are described as follows:

Portals: the values for ‗HL = (required length in mm)‘ and ‗HR = (required length in mm)‘, being left and right mast height, is the distance from the underside of the base plate to the underside of the bridge. The underside of the bridge is normally located 7500 mm above the rail level of the highest track, the portal is servicing. The underside of the base plate is positioned 30mm above the top of the pedestal to allow for base plate grouting. It is preferable to round up mast heights to 100 mm increments using the vertical position of the pedestal to make the required adjustments. For mast height documentation on portal structures refer Figure 72;

Cantilever masts: the value for ‗H =‘ is the distance from the underside of the base plate to the underside of the cantilever mast boom. The underside of the boom is normally located 7500 mm above the rail level of the highest track the cantilever structure is servicing. The underside of the base plate is positioned 30mm above the top of the pedestal to allow for base plate grouting. It is preferable to round up



mast heights to 100 mm increments using the vertical position of the pedestal to make the required adjustments. For mast height documentation on a cantilever structure refer Figure 73;

PP masts and Type 1 FSAM: the value for ‗H =‘ is the distance from the top of the pedestal to the top of the PP mast. The top of the mast is normally located 7500 mm above the rail level of the highest track the PP mast is servicing. The top of the pedestal is positioned to allow the mast height to be rounded to a 100 mm increment. For mast height documentation on a PP refer Figure 74;

HP masts and Type 2 FSAM: the value for ‗H =‘ is the distance from the underside of the base plate to the top of the mast. The top of the mast is normally located 7500 mm above the rail level of the highest track the structure is servicing. The underside of the base plate is positioned 30 mm above the top of the pedestal to allow for base plate grouting. It is preferable to round up mast heights to 100mm increments using the vertical position of the pedestal to make the required adjustments. For mast height documentation on a HP or FSAM, refer Figure 74 and Figure 75;

The mast height nominated on the Structure Diagram for SHS portals and PP masts does not represent the length of the section required to fabricate the structure. In the case of SHS portals the actual mast extends up to 500 mm beyond the underside of the bridge to allow for the two to connect. With PP masts the steel section extends to the bottom of the footing to support it during construction.

8.2.7 Track centres and track names

An important component of a Structure Diagram is the location of tracks that make up the cross section. The horizontal position of the tracks relative to one another, i.e. track centres, needs to be available at the location of all Structure Diagrams. Design track centres should always be used to draw up the cross section as these values are used to position masts, calculate bridge and boom lengths and determine the position of drop verticals. Track centres are provided on the Structure Diagram in the form of dimensions which are placed in line with the mast offset dimensions.

Each track shown on the cross section requires naming which should be consistent with the track designations given on the Electrical Loading Diagram and Layout Drawing. Minimal abbreviation of track names should be used when documenting a Structure Diagram but this will be dependent on the number of tracks and their track centres. In cases where a track has no design alignment the word ―existing‖ is to be added to the track name.

Track names label the centreline of the track being named. Typical track centre and track names are shown in Figure 72 to Figure 75.



Figure 72 : typical portal structure diagram

Figure 73 : typical cantilever mast structure diagram



Figure 74 : typical PP & HP structure diagram

Figure 75 : typical FSAM structure diagram



8.2.8 HTRL

Mast heights for all overhead wiring structures are measured from the rail level of the highest track (HTRL) being serviced by the PP, HP, Portal, Cantilever Mast or FSAM. The rail level of the highest track is then nominated on the Structure Diagram as the reference point or datum level. Figure 76 provides a diagrammatic explanation of the HTRL for a typical portal structure. Similar principles are applied for other types of structures.

Figure 76 : HTRL for a typical portal structure

The term ―rail level‖ has a precise definition. For a given track at a given location, it is the level of the top surface of the chosen rail, where the chosen rail is:

on straight track, the Down rail; on curved track, the inner rail (which, for existing track, is not necessarily the low

rail).

It follows from this definition that, in order to determine the ‗rail level‘ of a track, it is necessary to know something of the geometry of the track at that location, specifically the direction of curvature, if any.

Some examples of how the definition is applied:

on straight track, existing rail level is always given by the down rail, even if the existing up rail is lower at that location;

on curved track with little or no super (e.g. in a yard), the rail level is always given by the inner rail, even if the existing outer rail happens to be somewhat lower at that location.

For each track at a structure location, a design rail level and an existing rail level is determined from data provided by survey. The higher of these two levels is selected for each track, and the highest of these selected levels becomes the HTRL for the structure.

The HTRL may be either a design level or an existing level and is indicated on the Structure Diagram as follows:



HTRL (D) 88.957: where the rail level provided is the current design or proposed design reduced level given in metres to AHD;

HTRL (E) 27.560: where the rail level provided is the existing reduced level given in metres to AHD;

Examples of how to specify the HTRL on a Structure Diagram for various types of structures are provided in Figure 72 to Figure 75.

8.2.9 Drop vertical length, type and position

Drop verticals are present on both portal and cantilever mast structures and provide independent registration to the overhead wiring. The requirement of a drop vertical on a structure is specified by the electrical designer by indicating their requirements on the Layout Drawing, Loading Diagram and through the provision of a Drop Vertical Length and Position Table. It is the electrical designers‘ responsibility to ensure that the position of the drop vertical is clear of the train and pantograph kinematic envelope.

When specifying a drop vertical on a Structure Diagram three requirements need to be documented. These are:

Drop vertical length: the length of a drop vertical is determined by the structure design engineer using the drop vertical information provided by Electrical Design who specify the required vertical distance from rail level of a particular track to the bottom of the drop vertical. The drop vertical length is then calculated so that when it is attached to the underside of the bridge or boom the bottom is in the desired position. As a check the bottom of the drop vertical is usually located about 300mm below the contact wire.

The calculated drop vertical length is rounded to the nearest 0.1m and placed on the Structure Diagram in metres next to the drop vertical. The drop vertical length is followed by a two or three letter code that specifies the section size and configuration. An example of drop vertical length rounding is: - calculated lengths equal 2849 mm and 2850 mm, rounded to 2.8 m and 2.9 m respectively;

Drop vertical type: single and twin type drop verticals are specified by Electrical Design for use on portals and cantilevers. The section size that is currently used for drop verticals is a 150UC37 which is documented on two standard drawings. The first covering single drop verticals and the second covering twin drop verticals. As there are different structure types there are a number of different drop vertical attachment configurations for drop verticals. To enable the designer to specify the correct drop vertical, a coding system has been developed that is placed after the length to specify the drop vertical type required. Table 14 below explains what the coding represents and how it is applied to the different structures;

Drop Vertical Code Drop Vertical Type Relevant Structure Types

DS Single SHS Cant, SHS Portal, DC & DUB Portal

DSW Single DC Portals with walkways DT Twin SHS Cant, SHS Portal, DC & DUB

Portal DTW Twin DC Portals with walkways

Table 14 : Drop vertical coding

Drop vertical position: the position of the near side drop vertical face relative to the vertical track centreline is provided by the electrical designer. Using this information it is the structure designers‘ responsibility to locate the drop vertical using the Structure Diagram to convey the position. Drop verticals are usually attached to a new structure bridge before the bridge is installed, with final



adjustment undertaken after installation. The track side face of the mast forms a good reference point from which the drop vertical position can be measured in the field and it is for this reason that the drop vertical position is dimensioned from this point on the Structure Diagram. The dimension is calculated to the face of the drop vertical that is closest to the mast being utilized as the reference point. Only one position dimension is required for each drop vertical and this should be dimensioned from the nearest mast. On multiple track structures this can result in drop vertical locations being dimensioned from both masts. A check to ensure the drop vertical does not clash with the knee brace or other elements of the structure also need to be undertaken. Appendix G provides sketches showing non usable zones for each structure size and drop vertical type.

The calculated drop vertical position is rounded to the nearest 10mm. Stacked dimensioning is used when more then one drop vertical is dimensioned from the same mast. It is important to remember to account for the drop vertical width where applicable when calculating the position. A 150UC37 drop vertical which is the size specified on current standard drawings, has a width of 162 mm not 150 mm. An example of drop vertical position rounding is: - calculated position equal 4924 mm and 4925 mm, rounded to 4920 mm and 4930 mm respectively;

An example of how drop vertical length, type and position are documented for portals and cantilevers on a Structure Diagram can be found in Figure 72 and Figure 75.

8.2.10 Footings

Most of the standard overhead wiring structures contained in Appendix A have an associated standard footing drawing. When a structure size is nominated on a Structure Diagram the footing size is nominated by default as the associated drawing unless noted otherwise. Different types of footings, based on a variety of construction methods are depicted in each standard footing drawing. The hold down bolt configuration for each structure size is different so only the correct size steelwork can be installed. This helps to prevent the wrong size being installed in the field. The footing type to be used is usually determined by those responsible for construction in consultation with the design engineer. Some types of footing are not suitable in all locations while others are required for particular reasons. Footing types available along with advantages and disadvantages are:

Regular footing: consists of an excavated footing ranging between 1500 mm square and 1800 mm perpendicular by 2000 mm parallel to the track. The top of this footing is located at a minimum of 1000 mm below the lowest adjacent rail level to provide sufficient clearance for future formation reconditioning works without compromising the stability of the footing. The depth of the footing is determined by the foundation conditions at the site of the structure. A footing depth table on each drawing provides seven different foundation conditions and a corresponding footing depth. A qualified geotechnical engineer on site during footing construction verifies that the foundation material corresponds with the documented type in the table. If a geotechnical investigation consisting of a borehole has been undertaken at the proposed location of the footing then a depth can be determined from this information by the design engineer and noted on the Structure Diagram. As ground conditions can vary any footing depths determined in this manner which are not in close proximity to the borehole should be verified on site by a qualified geotechnical engineer.

A pedestal containing the hold down bolt arrangement for the structure is connected to the top of the footing by embedded reinforcement. Pedestals 900 mm or 1200 square or 900 mm perpendicular by 1200 mm parallel to the track are specified to make use of standard form shutters. Pedestals by default are centrally located on the footing but where tight clearances are encountered with services,



buildings or boundaries both the hold down bolt configuration and pedestal can be offset, in relation to the footing, to reduce the amount of room required beyond the mast. Methods for documenting offsetting of hold down bolts and pedestals are covered in Section 8.2.21 of this manual.

Regular footings have been the favored form of construction in the past but with the availability of small excavators and auger attachments the use of pile footings is increasing. Regular footings still have advantages when constructing around in-ground services or when rock is encountered that can not be augured by a small excavator. Services such as drainage pipes and cable conduits can be encased in a regular footing if the correct detailing is specified. A major disadvantage of this type of footing construction is the volume of excavated material that requires disposal;

Pile footing: is constructed using a pile with a diameter of 750 mm, 900 mm or 1200 mm and placing a pedestal containing the hold down bolt arrangement on top. A pedestal 900 mm square, 1200 mm square or 900 mm by 1200 mm parallel to the track are specified to make use of standard form shutters. The pedestal and holding down bolt arrangement are placed centrally on the pile.

The depth of the pile footing is determined by the foundation conditions at the site of the structure. A footing depth table on each drawing provides six different foundation conditions and a corresponding pile depth. A qualified geotechnical engineer on site during footing construction verifies that the foundation material corresponds with documented types in the table. If a geotechnical investigation consisting of a borehole has been undertaken at the proposed location, then the footing depth can be determined from this information by the design engineer and noted on the Structure Diagram. As ground conditions can vary any pile depths determined in this manner which are not in close proximity the borehole should be verified on site by a qualified geotechnical engineer.

Pile footings are becoming the predominant form of footing construction due to the advantages they hold over the regular type. Small excavators with auger attachments are able to achieve the required pile depth in both soil and weak rock. This reduces the amount of excavated spoil to be removed from site and simplifies the reinforcement cage size as the cage can be cut to suit the pile depth. The open area of excavation is reduced and it can be easily covered for safety before the concrete pour takes place. The reduced opening is also an advantage as it reduces the chance of destabilizing the track. On embankments a piled footing is preferred as it transfers the lateral loading to deep within the embankment. The effective pile depth on an embankment is measured below the point where 2000 mm of fill exists between the embankment slope and the centre of the pile.

A pile footing can be a disadvantage if obstructions below the surface or a strong layer of rock are encountered and the auger cannot penetrate. In these circumstances the footing can be converted to a regular footing where there is sufficient room to use a rock hammer.

For piling in an embankment fill containing boulders, which is a common occurrence, a good option may be to specify that a permanent steel casing be used. It is pushed down by an excavator with a special attachment, and any boulders encountered can be broken up while the casing protects the pile hole from collapsing. Once the casing reaches design pile depth the interior can be cleaned out by auger then the pile concrete is placed.

Footing in rock: is only to be used if specified by the design engineer on the Structure Diagram as it can only be used in certain location and for particular rock types. The footing consists of a pedestal containing the hold down bolt



configuration chased into the rock and further secured by the main reinforcement bars of the pedestal being anchored to the rock mass using cored holes and grout.

Footings in rock are only specified for use in Class I and Class II sandstone and shale. The rock class is to be verified on site by a qualified geotechnical engineer. These footings are not to be positioned on rock which is likely to be subjected to degradation by water such as cess drains and natural water courses. Consideration must also be given to future works such as formation reconditioning or trenching for cable or drainage installation, which may reduce the rock mass and its stability. For these reasons rock footings are usually only placed in cuttings where footings are required well above track level.

If a particular footing type is required, by design or requested by construction, than it should be nominated on the Structure Diagram by drawing the correct type of footing and labeling it with one of the footing type nominated above. Where the footing type determination is left to the field construction staff it should be drawn as a regular footing but left unlabeled. An example of how a particular footing type is nominated can be seen on the Structure Diagrams in Figure 72 to Figure 75.

A PP mast requires a piled footing. A HP mast can have a regular, pile or rock footing.

8.2.11 Features adjacent to the structure

A Structure Diagram must show sufficient information about the terrain beyond the structure to allow it to be used in the design process and during construction planning for determining aspects such as site access and possession requirements. All features such as services, troughing, cess drains, other structures and ground profile should be incorporated into the cross section of the Structure Diagram.

The location of services, the slope and the distance of the ground line beyond the structure will help determine the placement of footings and tops of pedestals during design and allow construction personnel to determine what size plant will be suited to construct the footings and erect the steelwork. As a planning tool the Structure Diagram can be used to help determine what footing locations can be constructed during non possession and possession times.

To provide this level of information on the Structure Diagram it is important that sufficient detail is collected in the field by the surveyor when the field work is undertaken. Information in two formats are usually required for undertaking overhead wiring structure designs, these are:

Survey cross sections; Detail Survey;

8.2.11.1 Survey cross sections

A survey cross section is required at each new overhead wiring structure location. Each cross section is to extend about 6 m beyond each proposed mast location and shall locate any ground line or track side feature and service it crosses. If a feature in the vicinity of the proposed footing location (within a two metre radius) is not cut by the cross section then the surveyor must note the perpendicular offset distance to the feature and its configuration. Each cross section must contain the following information.

Design and existing track levels for all tracks within the cross section; Design and existing track centres for all tracks within the cross section; Design and existing track superelevation for tracks within the cross section; Existing catenary and contact wires, anchor rod or span wire height within the

cross section;



When a feature such as an above ground service is located in the cross section the natural ground level at the base of the service shall be provided;

The width and/or size of any feature crossed by the cross section shall be provided;

In general the section is to extend 6 m beyond the mast of the new structure but must include the toe of any embankment or the top of any cutting that starts within the nominated 6 metres;

Some structure locations have specific cross section requirements. At these locations project specific requirements should be provided by the design engineer in tabulated form and marked up sketches of the preliminary Electrical Layout;

8.2.11.2 Detail Survey

At nominated structure locations additional survey information in the form of a detail survey (plan view) may be required to ensure that ground features, track side structures and equipment can be identified and avoided during the design process. The extent of the area requiring this detail survey shall be identified by the design engineer and described for each individual location in tabulated form and marked up sketches of the preliminary Electrical Layout.

All detail survey information is to be in Microstation V8i format with all relevant points strung together to create a cross section or plan view as required. The following criteria apply to all survey information requested:

The survey is to be in ISG or MGA and to AHD to match the track horizontal and vertical alignment models;

All point codes, symbols and levels used in the survey data and drawings shall be in accordance with RailCorp EP 0511 ―Detailed Site Survey Plan Symbols & Interpretation Guidelines‖;

The Microstation file is to contain levels with sufficient separation of features and data (reduced levels, text and line strings) to allow it to be manipulated for use in a Structure Diagrams;

The data for points surveyed (e.g. heights, point numbers and point codes) are to be on individual levels that contain no other information;

The cross sections are to be drawn at a natural scale and be in a model file that has metre master units;

The detail survey is to be in a model file with real world coordinates and have metre master units;

8.2.12 Anchor heights

Anchor heights provide information to the steelwork fabricator and construction staff so anchor attachment plates can be positioned at the correct height which is essential to achieve a good wiring overlap that does not cause flashes or damage the wire and pantograph. Using the anchor heights and reference track provided on the Electrical Loading Diagram, a height for the drilling point to attach the anchor plate on the mast is determined.

Two different methods are used to document anchor heights on Structure Diagrams. For fabricated masts the anchor heights are dimensioned from the underside of the base plate to the top drilling holes for the anchor plate attachment. Masts that are installed in the field and cannot have anchor plates holes pre drilled, such as PPs and existing structures that are converted to anchor structures, are site drilled to dimensions on the Structure Diagram which are dimensioned from a reference track.

The reference track given by Electrical Design on the Loading Diagram is the reference point, at the anchoring structure, from which the given anchor height is to be measured. In most cases the reference track is the one adjacent to the mast but in some situations



the reference track may be one of the other tracks at the structure location. This is most likely to occur when the track being anchored is not adjacent the mast and has a significant difference in rail level to the adjacent track.

To calculate the anchor height dimension for a fabricated mast the reduced level of the reference track is determined. As this will be the defined rail level and anchor heights are measured above the mean rail level half the track super elevation needs to be added. This level has the anchor height added, plus 0.085m when a moving anchor plate as detailed on drawing EL 0009443 is specified and 0.070m when moving anchor plate as detailed on drawing EL 0046204 is specified, to determine a level for the top of the drilling group. Subtracting the underside of base plate reduced level results in the dimension required for the Structure Diagram. This dimension is converted to millimetres and placed on the Structure Diagram between the mast and the mast height dimension. A typical example of dimensioning anchor heights from the underside of base plates can be found in Figure 72, Figure 74 and Figure 75. The anchor height dimension is used by the fabricator in conjunction with the standard steelwork drawing to provide the correct height attachment point.

For mast steelwork that is field installed from stock lengths, usually only PP‘s, the anchor attachment holes are not usually pre drilled as the steelwork is cut to length to suit the pile footing depth and the required accuracy for anchor heights is difficult to achieve. With these structures the anchor plate attachment holes are drilled after installation so the dimension on the Structure Diagram is documented from the reference track. As the reference point will be the defined rail level the dimension needs to have half the track super elevation added to the Electrical Design supplied value and an allowance for the distance the anchor bolts are above the anchor point. This dimension is placed on the Structure Diagram between the mast and the mast height dimension. A typical example of dimensioning anchor heights from a reference track can be found in Figure 74.

8.2.13 Anchor plate notation

Provision of anchor drilling heights on a Structure Diagram is only one aspect of detailing the termination of an anchor wire. An anchor plate, to attach the electrical termination arrangement to the mast, needs to be specified along with information on its orientation and nomination of what drilling arrangement on the mast is required for attachment of anchor plates and weight guides.

There are many combinations of anchor plates, structure size and anchor type that the anchor plate notation provides on the Structure Diagram. Set notation elements for each line in the anchor plate notation that must be followed are:

Wire run; is the name of the track that the wire run being terminated has been servicing. When a turnout or crossover wire is being terminated the track named in the anchor plate notation will not appear in the Structure Diagram cross section as the termination point (structure location) is always beyond the points of the turnout.

Anchor type; designates if the anchor attachment is to be fixed or moving. As moving anchors have weights, it allows other disciplines using the Structure Diagrams to consider their relevance during signal sighting and speed board location planning.

Anchor location; specifies the side of the mast (Sydney or country side) on which the anchor plate is to be attached. This notation is only required for Free Standing Anchor Masts, which have no guys and therefore lack the guy detail information which normally indicates the direction of anchorage.

Mast drilling; specifies the drilling pattern and configuration to be applied to the mast of the structure. This is particularly relevant when universal column masts are being utilized as anchor points because some drilling configurations, e.g. Type D2 drilling require holes in the web and Type D1 drilling requires flange drilling.



Anchor plate drawing; provides the number of the drawing to fabricate the required anchor plate. This reference is an electrical drawing but as the anchor plates require structural fabrication they are supplied with the structural steelwork and therefore referenced on the Structure Diagram. No other electrical arrangement details are to be shown on the Structure Diagram.

Anchor fitting; relates to the structure size thus providing key dimensions to be used to fabricate the anchor plate as each anchor plate drawing can be used for a number of different size structures.

The elements explained above have a number of options available and these are provided in Table 15. Examples of how the anchor plate notation is applied on a Structure Diagram can be found in Figure 72, Figure 74 and Figure 75. A comprehensive range of anchor plate notation is contained in Section 5.7 Anchor configurations.

Notation Element Options Available

Wire run ―Name of track the wire run is servicing‖ e.g. Up Main, X-Over

Anchor type Fixed or Moving Anchor location Sydney or Country Mast drilling D1, D2 or D3 Anchor plate drawing EL 0009428, EL 0009443, EL 0016592, EL 0016594,

EL 0046204 and EL 0366933 Anchor fitting 601/7, 601/8, 601/58, 358/61, 358/63, 358/73, 358/74,

358/75, 358/76, 358/77, 358/78 and 358/79

Table 15 : Anchor plate notation elements

Anchor plate notation is located on the Structure Diagram above the mast and anchor height dimensions. When there is two or more anchor points the notation applies to all locations provided the same anchor plate and fitting are required. If an auxiliary feeder is required in a regulated system at a moving anchor then it may require separate notation as the wire is usually fixed tensioned and does not require a moving anchor plate.

Batten plate locations on double channel portals have been positioned to avoid anchor plate locations for standard anchor heights of 6000 mm and 7000 mm when the bridge is placed at 7500 mm above the HTRL. If anchor heights specified by the electrical designer are significantly different then a check should be undertaken to ensure the anchor plate will not clash with batten plate locations.

8.2.14 Guy footings

At anchor wire termination locations where the mast is not designed to be free standing the majority of the tension loading applied is transferred to a guy footing. There are a number of different guy footings that can be specified on a Structure Diagram. These are:

Guy footing; is an excavated partially reinforced concrete anchor block with a reinforced 900 mm by 900 mm pedestal containing anchor lugs. The mass of the footing and the passive resistance generated due to it being below the ground provides sufficient capacity to counteract the anchor loads. Similar to regular mast footings the top of the guy footing must remain 1000 mm below the near track level to allow formation reconstruction works. This type of guy has similar advantages and disadvantages as the regular structure footing discussed in Section 8.2.10. The guy footing nominated on the Structure Diagram can be constructed from the details provided on the footing drawing.

Guy pile; consists of a 900 mm diameter pile with a 900 mm by 900 mm pedestal containing the anchor lugs. The anchor loads are resisted by the self weight of the footing and the lateral capacity developed by the pile. A guy pile has the advantage



of reduced spoil to remove from site and a greatly reduced risk of destabilizing the track.

Guy in rock; is a 900 mm by 900 mm pedestal chased into Class I or Class II shale and sandstone bedrock. The anchor lugs are cast into the pedestal and are extended to provide embedment into grouted cored holes to provide additional anchorage. The use of this type of guy is only specified by the design engineer and should be limited to locations where the rock mass will not be eroded or destabilized by future formation works or subject to water such as in cess drains. For these reasons, guys in rock, like footings in rock, are usually placed well above track level in cuttings.

Each type of guy footing comes in three sizes that increase in load carrying capacity. These sizes are nominated as G1, G2 and G3 with the capacity of each given in Section 5.8. The size of the guy is determined by the design engineer and will be documented on the Structure Diagram below the structure footing along with the side of the structure it is to be located. If a guy pile is footing depth different to the standard is required it will also be provided. Examples of guy documentation on a Structure Diagram are provided in Figure 72 where a guy pile in nominated for the down mast of the structure and a guy footing for the up mast. Figure 74 provides further examples.

The setting out of a guy is based on three dimensions which are only provided on the Structure Diagram when the designer wants to override the default values. The three setting out dimensions are:

X; defines the along track location of the guy with respect to the centreline of the mast at the structure location. The default value is usually the largest of the anchor heights, which will thus maintain the requirement that the guy rod slope does not exceed 45 degrees from the horizontal.

Y; defines the level to which the top of the guy pedestal is placed above or below the mast footing pedestal height. Common practice is to place both pedestals at the same height resulting in a default value of zero. Care should be taken to ensure the default value is not used if it is likely to contradict the maximum allowable pedestal height of 1000 mm.

Z; defines the distance from centreline of track to the centre of the pedestal. The guy footing is placed at the same track offset as the structure by default. If the angle of the anchor wire relative to the structure (in plan view) is significant the amount of radial load on the structure can be reduced by increasing the Z dimension to align the guy rods with the anchor wire. When undertaking this activity care should be taken not to block access road or obstruct cess drains. The amount of movement that is achievable is limited as the guy rod has a clevis fitting at both ends connecting to the anchor plate and anchor lug that will restrict movement. This problem may be addressed as follows: at the guy footing end, by orienting the footing in line with the guy rods (i.e. pointing to the mast); at the mast end, by specifying that a shackle be added into the connection between guy rod and mast.

As an alternative to using the default values for setting out guy footings, some projects use coordinates and reduced levels similar to the mast footing to locate the guy. This information is provided on the Structure Diagram below the guy notation information. This method should be used when the guy location is critical to ensuring the radial load on the structure does not become excessive. An example of this setting out method can be found in Figure 77.

At some structure locations in rock cuttings where the standard formation width has not been achieved, it becomes impractical to construct a guy as an enormous amount of rock would need to be excavated to install the guy and guy rods. An alternative to providing a guy is to use the rock face to attach an anchor bracket as detailed on the standard drawing. These locations need to be individually designed and documented on a



Structure Diagram. The guy anchor bracket is only to be used where sound sandstone Class I and Class II rock is present. An example of how a guy anchor bracket is documented on a Structure Diagram is given in Figure 78.

Figure 77 : sSetting out guy using coordinates

Figure 78 : Guy anchor bracket on rock face

8.2.15 Bridge splice

Overhead wiring structure bridges are fabricated from stock lengths of steel sections nominated on the standard steelwork drawings. For long span structures stock lengths can be joined using the specified weld detail to provide the required length.



The maximum practical length that a bridge can be fabricated without a field splice is governed by galvanizing and transportation limitations. Currently a bridge length 20.5 metres is the maximum that can be galvanized safely and transported without having to provide permits and escorts. A bridge length 18.0 metres or less provides fabricators with more galvanizing options. It should be noted that the ‗L‘ dimension given on the Structure Diagram is between mast centrelines and is not the actual length of the fabricated bridge component. Square hollow section bridges are shorter by the width of the mast and double channel portals are longer as they extend past the centre of the mast. These factors need to be considered when determining if a field splice is required.

Bridge splice details are provided on the standard steelwork drawings but the location of the splice needs to be specified by the design engineer on the Structure Diagram. The splice should be located outside the knee brace and preferably in an area of minimum moment. As a result the total bridge will usually consist of a long component and much shorter one as equal lengths would place the splice mid span and in the area of maximum moment. The splice plates must be located clear of drop vertical end plates and electrical fitting attachment points. Documentation of a splice on a Structure Diagram is shown in Figure 79.

Figure 79 : Typical bridge splice and access prevention grille

8.2.16 Access prevention grille

Structures are sometimes unavoidably located where access onto the structure by unauthorized persons has been made easy by placing masts and bridges where they can be climbed onto from other structures such as retaining walls or road bridges. Masts that can be easily climbed, such as double channel portals on platforms, also present a problem with unauthorized access. In locations such as these access prevention grilles are installed to protect the unauthorized person from potential harm and prevent disruption of the rail network.

A standard drawing detailing the access prevention grille for all standard structure bridges and masts is available. The location of the access prevention grille on the relevant structure is documented on the Structure Diagram. When placing an access prevention grille on the bridge of a structure it should be located beyond the knee brace so it cannot be bypassed using the knee brace to climb around it. If an access prevention grille is required on a mast then it needs to be located below the knee brace and will require two grilles to provide 360 degrees coverage. Standard grilles will need to be attached one above the other as they cannot be connected together back to back. The position of the



grille on the track side will need to be checked for clearance in relation to the General Kinematic Structure Gauge.

Typical documentation of access prevention grilles on a Structure Diagram can be found in Figure 79.

8.2.17 Notes

Each Structure Diagram drawing sheet must contain a set of notes that provides general information to the person constructing the structures giving advice on areas such as, but not limited to, track references, footing construction information and disposal of excavated materials. A set of standard notes used by RailCorp is provided in Figure 8.9. These notes should be added to if additional information is required for structures on the drawing.

Figure 80 : Typical structure diagram notes

On a Structure Diagram drawing the notes are located in the margin of the sheet above the title block. Within the margin area the notes are positioned above the references which are discussed in Section 8.2.18.

The notes are not to be used for providing electrical arrangement information as these are structural drawings and not usually available on site during wire rebuilds as the structures are constructed during preceding track possessions.



8.2.18 References

Structure Diagram drawings must provide References to other drawings associated with the project and relevant to the construction of the structure locations documented on it. References are to be shown in the order they appear below and cover the following areas:

All other Structure Diagram drawings associated with the project or deliverable section of the project. For larger projects, a drawing (e.g. Cover Sheet) containing a listing of all other Structure Diagrams should be provided. For smaller projects with more than two Structure Diagrams the first sheet should list all Structure Diagrams in the set above the references with a heading ―LIST OF DRAWINGS IN SET‖ and make reference to this first sheet in subsequence Structure Diagram sheets.

All the RailCorp standard drawings required to construct all aspects of the structures nominated on the drawing including both footings and steelwork.

All location specific detail drawings required to construct any structure nominated on that particular Structure Diagram drawing.

Any references to existing Structure Diagram drawings for existing structure that are to be reused and require modification.

References are to be placed below the notes in the margin of the drawing sheet and should be documented as shown in the example in Figure 81.

Figure 81 : Typical references

8.2.19 PP/HP table

When a project has a large number of single masts in the form of PP‘s and HP‘s then it becomes efficient to document these locations in tabulated form. Single masts that are used as anchor points and have guy footings are not to be included in the table as the information required to document anchor masts correctly is extensive and can cause confusion if put in tabular form. FSAM should also not be documented using this method as they require special information that can not be provided in a table. These types of structures need to be documented on individual Structure Diagrams.

The PP/HP table method of documentation consists of two components. The first component is an indicative Structure Diagram that provides a visual representation of any



structure location and expresses the design inputs in non specific terms. The indicative Structure Diagram is able to address all mast configurations by assigning different non dimensional inputs depending on which side of the track the single mast structure is located. The values ‗X1‘ and ‗Track 1‘ for a mast on the Down Side of a track and values ‗X2‘ and ‗Track 2‘ on the Up Side of a track.

Figure 82 : PP/HP table indicative structure diagram



Figure 83 : Typical PP/HP table



The second component of the documentation is the table containing the design inputs assigned to the individual structure locations. Each of the columns in Figure 83 are now described briefly:

Location; the structure number of the structure being documented is placed in this column. This column is never blank, unlike other columns in the table.

Track 1; the name of the track which the structure is to be placed on the Down Side of.

Track 2; the name of the track which the structure is to be placed on the Up Side of.

Mast type; the type and size of the mast to be installed. Choices are limited to PP2, PP3, HP2 and HP3. The design engineer may allow the constructor to choose between PP and HP types, in which case both types are nominated in this column e.g. PP2/HP2.

X1; the horizontal setout dimension from Track 1 to the centreline of the structure. X2; the horizontal setout dimension from Track 2 to the centreline of the structure. H; the height of the mast. For PP masts this dimension is from the top of the

pedestal to the top of the mast. For HP masts this dimension is from the underside of the base plate to top of the mast.

C; is the dimension above or below the rail level that the top of the pedestal is to be positioned relative to. If the pedestal is to be located below rail level then the ‗C‘ value will be negative. To position the top of a pedestal above rail level a positive ‗C‘ value is specified. A value of zero indicates that the pedestal is placed at rail level. If a reduced level is provided for the pedestal then this column should be left blank.

HTRL; the rail level of the highest track being serviced by the mast. If the design or existing rail level at the proposed structure is available then it should be provided in this column.

Top of Pedestal; the reduced level of the pedestal is placed in this column when a HTRL at the proposed structure location is known. If a reduced level of the pedestal is provided then the ‗C‘ column remains blank.

Easting; the easting of the centre of the mast is to be provided. Northing; the northing of the centre of the mast is to be provided. Remarks; any additional information that the design engineer feels is necessary to

convey to construction personnel about conditions at this location.

An indicative Structure Diagram and a PP Table should be placed on a drawing sheet that contains no other Structure Diagrams.

8.2.20 Title block

Setting out and filling in of the title block, signature block, amendment block and consultant title block shall be in accordance with the text and sample title block shown in the current RailCorp CAD Manual.

There are some specific requirements for OHWS projects when filling in the title block information. These are discussed below with reference to labeling shown in the sample title block given in Figure 84.

Location; is the name of the station closest to the structure being documented on the drawing. For a project that is undertaking the upgrade of a section of track the location should be named by using the two stations at the extremity of the works. In some cases, with RailCorp‘s approval, a railway location (e.g. Argyle) may be used instead of a station name.

Line and kilometrage; are determined in accordance with the designated lines within the RailCorp System. When multiple structures are documented on a drawing it becomes impractical to list all kilometrages. For this reason only the line needs to be nominated.



Figure 84 : Sample title block

Job description; consists of two lines where relevant information on the project is placed. The first line usually indicates what works the structures are associated with e.g. Overbridge or Underbridge Renewal, Turnout Replacement or a particular Overhead Wiring Modernisation Project. The second line should contain all the structure numbers documented on that particular drawing. If there is insufficient room the structure numbers can begin on the first line and continue onto the second. If a range of numbers need to be specified it should be broken up to provide at least one structure name in each kilometrage of track covered by the documentation.

Drawing type; the most commonly used is ―Structure Diagram‖ but when details are required other types of drawings need to be specified. The correct drawing type from Table 16 should be placed in this line of the title block.

Drawing Types

ALIGNMENTS ARCHITECTURAL DETAILS BAR SHAPES DIAGRAM CIVIL WORKS CONCEPT DESIGN CONCRETE DETAILS COVER SHEET CROSS SECTIONS DETAILS FOOTING DETAILS GENERAL ARRANGEMENT LAYOUT MARKING PLAN MISCELLANEOUS DETAILS NOTES OPTIONS PRECAST CONCRETE DETAILS PRECAST REINFORCED CONCRETE DETAILS PRECAST REINFORCEMENT DETAILS PROPOSAL REINFORCED CONCRETE DETAILS



SECTIONS SETTING OUT (& DETAILS, IF REQUIRED) STEELWORK STRUCTURE DIAGRAM SKETCH ASSEMBLY DETAILS STAGING

Table 16 : Bridges & structures drawing types

8.2.21 Special details

At some structure locations the specified structure type and size nominated on the Structure Diagram may require a small modification made to a component as the structure may be being used for a purpose outside what is detailed on the standard drawing. In many cases the addition of a special note or a small detail used in conjunction with the standard drawing will provide a satisfactory result.

On projects where the number of these special details is minimal and would not be enough to fill a special detail drawing, they can be documented on the Structure Diagram drawings. The space above the notes and references in the margin is often the best location to provide the details.

A detail symbol is placed around the component requiring modification, e.g. base plate and/or footing pedestal, making a suitable reference to the documented special detail. Examples of special details are:

offset (from mast centreline) the footing and/or pedestal and/or base plate and hold down bolts to achieve additional lateral clearance due to some obstruction preventing the footing being placed further out from the track centreline. An example of how these would be documented can be found in Figure 85, Figure 86 and Figure 87.

Figure 85 : Structure diagram showing offset footing and pedestal detail



Figure 86 : Typical offset footing and pedestal special detail documentation

Figure 87 : Structure diagram showing offset footing note & special base plate

the addition of more anchor bolts to a footing and baseplate to resist forces in the out of plane direction caused by a bridge anchor loading that does not have a guy which is being resisted by the mast acting as a free standing structure. An example of how this special detail would be documented can be found in Figure 88 and Figure 89.



Figure 88 : Structure diagram showing additional anchor bolts

Figure 89 : Typical additional anchor bolt special detail documentation

8.2.22 Special detailing referencing multiple standard structures

On some occasions a standard structure is not suitable at a particular location but a combination of a number of components from more than one standard structure can be used to provide a non standard structural solution without producing a new drawing.

The Structure Diagram must be very clear about what changes or additions need to be made to produce the desired structure. In most instances the base structure type is nominated as described in Section 8.2.2 and the elements that require amendment or addition are highlighted by using a detail symbol referencing another standard providing the fabrication or construction detail required.

An example of using this method for detailing a non standard structure would be when a portal is loaded in a manner that requires additional out of plane strength or serviceability



capacity in the masts. As the universal column used in the masts is orientated in the weak direction it becomes the governing component within the structure. In normal circumstances an anchor plate would be placed on the mast, just below the bridge, and support provided via a guy footing and anchor rods. If this situations occurs on a platform or obstructions prevent guy footings being installed the mast strength may need to be increased by converting it to a SHS section for example.

The portal is constructed using details from two standard structure types with the same section designation, e.g. 300 SHS Portal and Cantilever Mast. As an example the structure would be nominated as a ―Special 300 SHS Portal‖. The portal bridge would be fabricated as detailed on the 300 SHS Portal Steelwork Drawing using the ―L = ‖ dimension. The Structure Diagram would indicate a detail referencing the 300 SHS Cantilever Mast drawing for modifications to the bridge ends for connection to the mast. Masts, knee braces and footings are fabricated and constructed in accordance with the 300 SHS Cantilever Mast drawings. Referencing described above is placed on the Structure Diagram. Effectively, the structure becomes a portal constructed by the joining of two cantilever masts.

A typical example showing how this type of structure would be detailed and documented on a Structure Diagram is depicted in Figure 90.

In referencing these other standard drawings a structure can be altered without the need to produce new detail drawings. However, it must be noted that if the designer takes an element from a standard drawing and nominates it in a special application (for which it may not have been originally intended), the designer becomes responsible for the structural integrity of the element and must carry out all necessary calculations to ensure it is structurally adequate.

Figure 90 : Special detailing referencing multiple standard structures

8.2.23 Multiple span portals

In locations where a portal with multiple spans is required (this includes the addition of a cantilever span) the standard overhead wiring structure drawings make provision for this configuration by the addition of extra notation on the Structure Diagram.



When using SHS portals in a multiple span situation there is the flexibility to have the bridge in each span at a different height. This allows tracks where grade separation occurs, and where there is room between tracks for intermediate mast(s), to be registered with a structure crossing all tracks, making use of common footings, but with different bridge and or boom heights. This configuration allows the drop verticals to be kept at a reasonable length and comply with deflection requirements. When a multiple span portal is used certain additional information is required to be included on the Structure Diagram.

The standard SHS portal drawings have a marking diagram which indicates what dimensioning is required for a multiple span structure. Values for ―HL = ‖ and‖ HR = ‖ are given for the extreme left and right mast heights which are fabricated from the single mast detail. Internal masts are fabricated from the multi mast detail which require drilling for bridge attachments on both faces and therefore potentially requires two dimensions, ―H = ‖ and ―Y = ‖, as each bridge could be at a different height. The ―Y‖ dimension is always the smaller and if the bridge heights are the same, i.e. ―H‖ = ―Y‖, only a value for ―H = ‖ is shown on the Structure Diagram.

When a portal structure includes a cantilever a multiple mast detail is required. Two dimensions are required if the bridge and boom heights differ, ―HL = ‖ or ―HR = ‖ and ―Y = ‖, but if they are at the same height only ―HL = ‖ or ―HR = ‖ is specified on the Structure Diagram.

A multiple span structure which includes a cantilever must have stiffeners welded into the mast where the boom connects and the boom length dimensioned ―LB = ‖ placed on the Structure Diagram. A kneebrace must be used with a cantilever of a multiple span portal. A portal mast with a cantilever and kneebrace only is not to be used as a standalone structure.

Figure 91 provides a typical example of a multiple span SHS portal Structure Diagram with a cantilever boom ―span‖. Other examples can be found in Appendix B.

Figure 91 : Typical multiple span portal – showing single portal span plus cantilever “span”



Multiple span portals constructed using double channel portal sections are less flexible as the bridge connects to the top of the mast resulting in all spans being at the same height. Care needs to be taken to ensure that drop vertical lengths do not become excessive when used on grade separated tracks.

The extreme left and right masts are dimensioned ―HL = ‖ and ―HR = ‖ on the Structure Diagram with intermediate masts labelled ―H = ‖. The bridge of a double channel portal can be configured as continuous over an internal mast or can have a joint at the mast. The configuration used will be dependent upon construction sequence and possession availability and it is important that the type of mast connection is specified on the Structure Diagram.

A cantilever can be utilised with the double channel portal multiple span arrangement provided a continuous bridge connection is used at the mast connection in combination with a kneebrace. The length of the cantilever in nominated by ―LB = ‖ on the Structure Diagram.

8.3 Standard OHWS drawings

RailCorp has a set of OHWS standard drawings covering both steelwork and footing details. It is intended that these drawings be referenced on the Structure Diagram drawings to provide all the required details for steel fabrication and footing construction.

The standard drawings have evolved over time and are updated to include changes in industry fabrication and construction methods. RailCorp is responsible for the updating of these drawings and values the input from anyone that can suggest improvements that can be made.

For the majority of structure locations a standard OHWS can be nominated. In some instances small modifications to the standard structures are detailed on the Structure Diagram which allows the standard structure to be specified. These modifications are discussed in Section 8.2.21 and Section 8.2.22.

On rare occasions when a standard structure will not suit the particular location a one off structure design is required. Approval to use a non standard structure must be obtained from the Chief Engineer Civil. The requirements for this type of structure are discussed in Section 8.4.

A number of reasons exist as to why standard structures are the preferred solution and new types of structures are not easily introduced into the rail system. These are:

The use of a set of standard structures allows steelwork fabrication, footing construction and installation personnel to gain an understanding of each type and become very efficient at producing or installing each OHWS component.

Details developed and proven over time which satisfy both inspection and maintenance requirements are incorporated into the standard drawings so the infrastructure is cost effectively maintained.

Using only a defined set of standard structures ensures that electrical fitting types are minimized and the number and types of spares required are also kept to a minimum.

It is in the design engineers‘ and RailCorp‘s best interest to make use of standard structures for as many locations as possible. An added advantage is that the amount of documentation required for a project is reduced.

A list of RailCorp standard overhead wiring structure drawings is provided in Appendix A. Amendments to these drawings will occur from time to time therefore it is the Designer‘s responsibility to check for the current drawing in the RailCorp Plan Room.



From time to time RailCorp will develop new standard overhead wiring drawings for use on projects. These drawings will be added to the list in Appendix A when the manual is next updated. The existence of new standard drawings will also be advertised through other methods within the Chief Engineers Division.

8.4 Location specific detail drawings

When the only solution for a structure is to produce a one off design for a specific location, as no standard structure can satisfy the design requirements, then approval to introduce a new style of structure into the system must be obtained from the Chief Engineer Civil.

In developing a new structure a number of design aspects must be applied where ever possible. These are:

The structure should be designed using elements of the same size as those on existing standard drawings. This will reduce the need for Electrical Design to produce new fittings for attachment to the mast and bridge of the structure. This approach also allows for the use of standard drop verticals on these structures.

The design should incorporate as many of the standard drawing details as possible. Elements such as base plate detailing, mast to bridge connections, bridge splices, knee braces and welding details are all areas that have been developed over time and should be progressed to new structure designs.

Special attention needs to be paid to inspection and maintenance requirements. All new types of overhead wiring structures are to take into account the ability to access the structural components for inspection and maintenance purposes. Components, materials and finishes should be chosen to minimize future maintenance due to the close proximity of the structures to the overhead wiring and the tracks.

The design of new overhead wiring structures are to take into account construction constraints, particularly live operating conditions and track possession constraints.

Footings for location specific steelwork drawings should be nominated as a standard structure footing drawing where possible as this will reduce the amount of new documentation required. Where a standard footing drawing can not be utilized the location specific footing design should also adopt as many features as possible such as pedestal size, hold down bolt size and configuration.

A location specific footing will often need to show the specific footing depth required as designing the footing for a number of foundation conditions may not be feasible. In order to do this geotechnical design parameters for the location will be required.

To minimize maintenance, overhead wiring structures are to be designed and fabricated using smooth, clean faced section without a proliferation of small members, fittings and metal to metal interfaces. In addition the following design criteria will also apply:

each structure shall be designed as a stand alone independent structure, except at anchor locations where adjacent masts may sometimes need to be connected using guy rods.

the minimum thickness of major steel structural components is to be 8mm. steel structures and fittings are to be galvanized, unless approval is given by the

Chief Engineer Civil to use alternative coatings e.g. coatings to meet heritage requirements.

the minimum size of fillet welds is to be 6 mm. designs must ensure that moisture and debris collection pockets are not created. the structures are to be designed for a serviceable life of 100 years.

The level of documentation for both steelwork and footing location specific drawings is not to be less than that found on similar standard drawings. These drawings will be used



for steelwork fabrication and on site footing construction and need to provide the same level of detail as a standard drawing so the same quality of workmanship is achieved.

All drawings are to comply with the requirements of the RailCorp CAD Manual and relevant Australian Standards. Completed drawings are to be in Microstation format utilizing the RailCorp designated levels and modelled at real size in an appropriate model space with referencing and scaling into a real size drawing sheet.

A soft copy of any location specific drawing needs to be supplied to RailCorp in Microstation V8 format when it is submitted.

8.5 Documenting modifications to existing OHWS

Whenever it is structurally and economically feasible, existing overhead wiring structures are reused in overhead wiring projects. These structures have usually been documented previously as part of another project and have a Structure Diagram giving structural details such as structure size, footing size, location and drop vertical and anchor configurations. The structure should be galvanised and showing no signs of corrosion or major damage. The structure must have been assessed by the design engineer to have a remaining design life, both strength and serviceability, acceptable to the project.

When a project involves reusing an existing overhead wiring structure and that structure requires structural modification a Structure Diagram showing the required changes needs to be produced as part of the documentation for the current project. Some typical structural modifications that require documentation are:

New, relocated or removed drop verticals; Addition or change in anchor plate type, drilling height and guy footing; Replacing a damaged mast or under strength bridge section; Footing strengthening or repair works; Extension or shortening of the structure;

In some large projects staged construction works are necessary as multiple track and overhead wiring configurations are required. Structure Diagrams produced for these staged works often consist of temporary and final configuration structures. The final structure may be used in intermediate stages in a temporary configuration. When documentation of the final configuration occurs these structure are ―existing‖ as they have been constructed early on in the project and now require modification. In these circumstances the structures are documented as ―existing‖ structures but all structural details from the previous staged works are carried through into the final configuration. This requirement is necessary because in large projects the staged or temporary works are not submitted to RailCorp for retention as only the final configuration drawings submission is required. If information is not carried through the staged works vital infrastructure information will be lost.

During construction of the final overhead wiring configuration some structures could be documented as ―existing‘, as they were early or staged worked structures, but in reality form part of the project. These types of large capital projects require ―As Built‖ drawings to be produced and it is during this process that all ―existing‖ structures, new to the project but documented as early or staged works, have line work converted to that of new works and any reference to ―existing‖ components removed.

Documentation of an existing structure is undertaken using the same detailing as required for new structures explained in Section 8.2 of this manual with the following modifications/exceptions to ensure the design intent is conveyed to construction staff:

Use of line thickness and types; Labelling of structure and components;



Referencing of existing Structure Diagram.

8.5.1 Line thickness and types

To clearly identify between structure components that are new, existing to remain or existing to be removed on a Structure Diagram different line thickness and types should be utilised. RailCorp uses Microstation V8i to undertake drafting of Structure Diagrams and line weights (WT =) are used to represent line thickness. Line weights WT = 0, WT = 1 and WT = 2 represent line thicknesses 0.18 mm, 0.25 mm and 0.35 mm respectively. These are the plotted line thickness of a full size drawing sheet at a scale of 1:1. The following line weights and types are to be used when documenting modifications to an existing structure:

New components or work – Solid line work with WT = 2; Existing structure components to remain – Solid line work with WT = 0; Existing structure components to be relocated – Medium length dashed line work

with WT = 1; Existing structure components to be removed – Short length dashed line work with

WT = 0.

An example of how this line work would be applied to a Structure Diagram documenting modifications to an existing structure can be seen in Figure 92 and Figure 93.

8.5.2 Labelling of structure and components

In addition to line thickness and line types it is also a requirement that discrete components are labelled as ―new‖ or ―existing‖ on the Structure Diagram. The size of the original structure should be labelled, e.g. ―EXISTING 250 UC PORTAL‖, in the same location as required in Section 8.2.2.

If the structure has drop verticals they should be labelled according to what is required of these components, e.g. ―NEW‖, ―EXISTING TO REMAIN‖, ―EXISTING TO BE RELOCATED‖ and ―EXISTING TO REMOVED‘. Drop vertical type, length and location as required by Section 8.2.9 is to be added to the new and relocated drop vertical. The type and length of an existing drop vertical to remain in the current location should be provided to allow Electrical Design to code the layout.

If the existing structure has anchor plates and drilling heights and these remain unchanged then a note is added to the Structure Diagram where anchor plate notation would normally be placed ―ANCHOR PLATES TO REMAIN‖. In some instances a fixed or moving end of a wire run may need to be swapped which will require changing the anchor plates. If the anchor heights remain the same a simple note stating ―CHANGE ANCHOR PLATES‖ followed by the new anchor plate notation as required by Section 8.2.13 is placed on the Structure Diagram. Should both the anchor plates and drilling heights need to be changed complete anchor plate height and notation in accordance with Section 8.2.12 and 8..13 are placed on the Structure Diagram along with a note ―REMOVE EXISTING ANCHOR PLATES‖. A combination of existing anchor plates with new drilling heights is also possible and should be documented with new anchor drilling heights. Care needs to be taken to ensure new anchor height drillings allow sufficient clearance to the existing anchor plate holes.

When an existing anchor point is reused ―as is‖ or modified consideration needs to be given to the guy footing that is currently in use. Old style guys designation such as M2 and M4 do not have the same capacity as G1, G2 or G3 guys currently used.

Any new components added to the structure such as a mast replacement, a new mast to allow a bridge extension or a complete bridge replacement and any kneebrace required should have the words ―NEW‖ placed in front of the notation.



Examples of new component notation on a Structure Diagram for a modified existing structure can be found in Figure 92nd Figure 93

Figure 92 : Existing OHWS drop vertical modifications

Figure 93 : Typical modifications to an existing OHWS

8.5.3 Referencing of existing Structure Diagram

To enable the existing structure details to be retrieved for future reference the Structure Diagram drawing for the existing structure, before it was modified and became part of the new project, must be referenced on the new Structure Diagram drawing sheet. Existing Structure Diagram drawing references are placed after other references as required by Section 8.2.18.



Appendix A List of standard OHWS drawings

DRG No OHWS DRAWING

CV 0373001 PP2 MAST AND PP3 MAST STEELWORK AND FOOTINGS CV 0373002 HP2 MAST AND HP3 MAST STEELWORK CV 0373003 HP2 MAST AND HP3 MAST FOOTINGS CV 0373004 200 SHS PORTAL STEELWORK CV 0373005 200 SHS PORTAL FOOTINGS CV 0373006 250 SHS PORTAL STEELWORK CV 0373007 250 SHS PORTAL FOOTINGS CV 0373008 300 SHS PORTAL STEELWORK CV 0373009 300 SHS PORTAL FOOTINGS CV 0373010 250 SHS CANTILEVER MAST STEELWORK CV 0373011 250 SHS CANTILEVER MAST FOOTINGS CV 0373012 300 SHS LIGHT CANTILEVER MAST STEELWORK CV 0373013 300 SHS LIGHT CANTILEVER MAST FOOTINGS CV 0373014 300 SHS CANTILEVER MAST STEELWORK CV 0373015 300 SHS CANTILEVER MAST FOOTINGS CV 0373016 300 DOUBLE CHANNEL PORTAL STEELWORK CV 0373017 300 DOUBLE CHANNEL PORTAL FOOTINGS CV 0373026 GUY FOOTINGS CV 0373027 GUY PILE AND GUY ROCK FOOTINGS CV 0373028 DS DROP VERTICAL AND DSW DROP VERTICAL

STEELWORK CV 0373029 DT DROP VERTICAL AND DTW DROP VERTICAL

STEELWORK CV 0373030 FREE STANDING ANCHOR MASTS STEELWORK AND

FOOTINGS CV 0373044 REPAIR FOR EXPOSED MAST FOOTINGS CV 0373046 CUTTING BRIDGE SUPPORT REPLACEMENT TYPE 1 AND

TYPE 2 E1- 437 380 DOUBLE CHANNEL PORTAL – STEELWORK E1- 438 380 DOUBLE CHANNEL PORTAL – FOOTINGS E1- 448 300 DOUBLE CHANNEL SIGNAL OR FEEDER STRUCTURE –

STEELWORK E1- 449 300 DOUBLE CHANNEL SIGNAL OR FEEDER STRUCTURE –

FOOTINGS E1- 450 DOUBLE CHANNEL FEEDER & SIGNAL STRUCTURE –

WALKWAY AND BALUSTRADE STEELWORK E1- 451 DOUBLE CHANNEL FEEDER & SIGNAL STRUCTURE –

LADDER AND CAGE STEELWORK E1- 452 SIGNAL CAGE STEELWORK E1- 453 LADDER LANDING FOOTING E1- 454 410 DOUBLE UB PORTAL – STEELWORK E1- 455 ACCESS PREVENTION GRILL STEELWORK E1- 456 460 DOUBLE UB PORTAL – STEELWORK CV 0047941 CANTILEVER SIGNAL STRUCTURE – STEELWORK CV 0055980 250 SHS DOUBLE CANTILEVER MAST – STEELWORK CV 0142949 FOOTING IN RETAINING WALL CV 0144833 BOXED FREE STANDING ANCHOR MAST – MAST AND

FOOTING DETAILS CV 0465528 GUY BRACKET ON ROCK FACE CV 0364937 DOUBLE CHANNEL FEEDER & SIGNAL STRUCTURE –

BALLUSTRADE GATE AT SIGNAL CAGE STEELWORK



Appendix B Example structure diagram drawings



Appendix C Wind loading calculations on overhead wiring

This page has been left intentionally blank as Appendix C will be added to the manual during a subsequent revision.



Appendix D Wind loading calculations on standard structures

This page has been left intentionally blank as Appendix D will be added to the manual during a subsequent revision.



Appendix E Wind loading calculations on feeder cables

This page has been left intentionally blank as Appendix E will be added to the manual during a subsequent revision.



Appendix F Microstran steel design restraint values

This page has been left intentionally blank as Appendix F will be added to the manual during a subsequent revision..



Appendix G Drop vertical position restrictions

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