Changes in TG 20 13

TG20:13 The Changes

TG20:13

Introduction and background to TG20:13

The NASC Suite of Documents

Legal Framework and Endorsements

TG20 Compliant Scaffolds Types

Wind

Ties and Anchors

Summary

Acknowledgement to the NASC

What is TG20?

TG20 represents the general rules of the scaffolding industry. It is mainly a technical document, and therefore not very readable.

It is aimed at tube and fittings, but a number of aspects ( eg foundations, board supports, scaffold boards, access) equally apply to systems.

Calculations would be required for every tube and fittings scaffold without TG20. It provides standard configurations

It can be considered the industry Code of Practice.

Purpose of New Guidance

Previous versions of TG20 have permitted only a narrow scope of Basic or Standard Scaffolds without design.

One of the main objectives of TG20:13 is to reduce the number of designs required, and enable the rules to be understood and applied without recourse to specialists.

It is in many ways a new set of rules.

The CISRS Basic Scaffold Inspection Course will now run to 3 days.

The eGuide software gives better results than the Operational Guide.

Introducing TG20:13

A comprehensive guide to good practice for tube and fitting scaffolding

TG20: 13 Changes

1. Now includes NASC SG and TG document content 2. Wind code now more specific from BSEN 1991-1-4 3. New windmap ( Operations Guide explains types) 4. TG20 Compliant Scaffolds explained 5. TG20 Operations Guide 6. Choice of Limit State or Permissable Stress in design approach. 7. Faade Bracing can be in single bay 8. Scaffold designations unchanged but only part of the story 9. Doubled standards now specifically mentioned 10. Transom tubes now have 25mm tolerance through the coupler. 11. Telescopic Transoms encouraged 12. Detailed info on use of Hop-Up Brackets 13. Band and Plates now mentioned 14. 2.4m Bays only permitted in Operational Guide, not 2.7m. 15. More emphasis on 900mm board spacings on 3Kn Class 4 16. Laminated and plastic boards included, plastic can overhang 180mm, not 150mm. 17. Max span of boards does not mention 50 or 63mm boards, just scaffold boards 18. Readylok/ Prefabricated Transom Units now included 19. Lift Shaft Towers added

20. Structural Transoms included 21. Transom couplers : no longer refers to sheeted scaffolds needing right angle or swivels, but TG20 compliant 22. Short boards dimension 2.15 not 2.13m 23. Use of Sleeve Couplers : Joints should be made with sleeve couplers, but ok in Standards, qualified

TG20: 13 Changes

24 Plan Bracing wording expanded to explain

25 Guardrails should use right angle couplers, not swivels or putlog couplers

26 Single Guardrails ok on unboarded lifts.

27 Guardrail height defined as 950 to 1260 if scaffold boards as toeboards (?)

28 Extending platform by 6 ft still ok, design if longer

29 New Cantilever Platform wording

30 Extensive New Tie text, inc sheeting options and their effect.

31 More tie classes: now 4 ( class B)

32 Tie details no longer in Design Guide, but Operations Guide

33 ( minimal re-use of some anchor types in OG)

34 Abnormal facades: inspect with teleboom

35 Rakers: more stringent requirements for external Rakers, inc wing bracing, resistance to uplift.

36 Access is mainly in the Operations Guide

37 Access hierarchy: integral ladder bay may be substituted

38 Ladder Towers projecting beyond the scaffold are a special case

39 Pavement Lifts major new guidance eg modified ties not mandatory

40 Openings and bridges have much more guidance

41 Bridging includes 750mm beams

42 Internal and external faade bracing required around openings

43 Minimum beam structural properties now included

TG20: 13 Changes

44 Loading Bays: now can be 4.0m, not 3.0m 45 Loading Bay Gates now included 46 Loading Bays which project beyond the faade are special cases 47 Guardrail wording now ensures protection at all times 48 Ladder beams now stated as 3.05m, not 3.35m 49 Birdcages : definition no longer multiplicity of standards, but a grid 50 New load classes 51 Dimensions now relate to load classes of birdcages 52 can be wider than 2.1m with ladder beams used 53 More birdcage illustrations ( Operations Guide has far more bracing details) 54 Indoor birdcages now refer to BSEN 12811 for wind 55 Overturning factors of safety now 1.5 not 1.2 56 Single lift birdcages :brace one in 4 bays. 57 The maximum number of unbraced internal bays is governed by the number of lifts 58 Access Towers new 0.75kN load class 59 Outriggers mentioned for towers 60 Tied Towers have new text: ? tied every lift? 61 Mobile Towers have no TG20 compliant designs ( some info in Design Guide) 62 Design assumptions for internal and external towers stated 63 Limited wind conditions for compliant towers 64 ( Wind Management system in Op Guide) 65 At least 2 lifts of external towers should be boarded to resist overturning 66 Public Access Staircases now more fully detailed, inc references 67 More details from BSEN12811 on Tube and Fittings Stairs.

TG20: 13 Changes

68 Foundation Loadings provided to aid clients 69 Tolerances are emphasised 70 Special Scaffolds not in Operational Guide 71 Node point restraint mentioned 72 Protection Fans: statement of general limitations 73 New Fan Standard is coming 74 Stair Towers: greater revised text, same loadings 75 Dimensions from BSEN 12811 now included. 76 Staircases No toeboard requirement unless 77 Cantilever scaffolds : similar text, but more specific about the way load is applied to the structure. 78 Safety during erection now included. 79 Lifting Gantries: unchanged, but CAD mentioned 80 Temporary Buildings : Out, now in TG9 81 Definition of Class A in Op Guide is fittings, not paint drips 82 Class A Fan illustration no longer wire shown 83 Class C Fan : vertical drop 6m, not 10m 84 Decking: Safety netting now included 85 Projecting of Fan included ( limited in OG?) 86 Pavement Frames : much more detail 87 Identification of EN74 Couplers

Legal Framework and Endorsements

11

Schedule 3 part 2 additional requirements for scaffolding

7) Strength & stability calculations for scaffolding shall be carried out unless a) A note of calculations, covering the structural

arrangements contemplated is available; or, b) It is assembled in conformity with a generally

recognised standard configuration.

Work at Height Regulations 2005

12

HSE Support

The Work at Height Regulations 2005 require that strength and stability calculations are carried out for scaffolds unless they conform to a recognised standard

HSE is pleased to acknowledge that TG20 has been

written by NASC to provide such a standard

Heather Bryant, Chief Inspector of Construction Health and Safety Executive

13

UKCG Support

We applaud and support the work of the NASC which will no doubt result in safer scaffolding

The UKCG recommend the adoption and standardised use of TG20:13 both within and outside the construction sector.

Stephen Ratcliffe,

Director UK Contractors Group

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TG20 Compliant Scaffolding

TG20 compliant scaffolds have been designed by structural calculation in accordance with BS EN 12811.

Design advice should be sought for any scaffold outside of the scope of TG20 Compliant Scaffolding.

TG20 compliant scaffolds were previously referred to as Basic or Standard Scaffolds.

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TG20 Compliance Sheets

Demonstrates compliance and that bespoke design is not required.

Typical Scaffolds included in TG20:13 Operational Guide (Chapter 03).

Wider variations included in the TG20 eGuide.

Design advice must be sought for any scaffold outside the scope of a TG20 Compliance Sheet.

What is a Basic Scaffold?

Main requirements: Double row of Standards, Ledger Bracing Faade Bracing every 6 bays Conforms to Table 1: Load Classes, Bay lengths, Widths. Only two working lifts: one 100% loaded, other 50% loaded Max lift height 2.0m No loading of materials by mechanical means Wind Loading factor S no greater than 40. Alternate pairs of Standards ledger braced Vertical ties spacing not to exceed 4m ( 2 lifts) Faade bracing is across two bays. Otherwise Plan Bracing has

to be fitted

Designed Scaffolds Per HSE

Dead / Flying/ Raking Shores

Cantilevered scaffolds

Truss-out Scaffolds

Access Birdcages

Faade retention

Buttressed free-standing scaffolds

Temporary roofs and temporary buildings

Loading Bays founded on the ground

Mobile and static towers outside base/height limitations

Free standing scaffolds outside base/height Limitations

Temporary ramps and elevated roadways

Staircases and fire escapes

Spectator Terraces and Seating Stands

Bridge scaffolds

Towers requiring guys or ground anchors

Pedestrian footbridges or walkways

Slung and Suspended scaffolds

Protection fans, Nets and Pavement Frames

Power line crossings

Lifting gantries and towers

Sign board supports

Temporary Storage on Site

18

The Operations Guide incorporates aspects of the old Technical Guidance and the SG and TG NASC series.

The New TG20 Guides

19

The Operational Guide

Conversational, readable style Lots of good illustrations Incorporates elements of Design, Safety and Technical

Guidance documents plus eGuide references.

20

TG20 Compliant Structures

21

TG20:13 Compliant Scaffold Types

Tied Independent Scaffolds Free-Standing Independent Scaffolds Towers Interior Birdcages Tied Putlog Scaffolds Loading Bays Ladder Access Towers Chimney Scaffolds Bridging with Beams Reinforced Transom Units ( Readylok) Light Duty Protection Fans Pavement Lifts Cantilevered Access Platforms

PlusTimber Frame Scaffolds are now in the CISRS Inspection course

22

Compliant Scaffolding Types

Tied Independent Scaffolding

23

Independent Scaffolds

Includes sheeted, debris netted and non-sheeted. Operational Guide covers scaffolds up to 16m height, but the eGuide

extends this up to 50m.

Faade Bracing: Single bay bracing is sufficient to avoid Plan Bracing. Maximum bays size restricted to 2.4m

Guardrails should employ right angle couplers, not Putlog Couplers Wider choice of decking materials Emphasis on Structural Transoms Doubled Standards have new section

24

Lift Heights and Headroom

TG20 Compliance Sheets allow lifts up to 2m

Compliant Scaffolds, however, can be determined in the TG20 eGuide up to 3m

25

Tube

TG20 Compliant Scaffolds only permits the following types of tube to be used:

BS EN 39 type 4 (4mm) galvanised steel tubes or equivalent

High-tensile galvanised steel tubes with a diameter of 48.3mm, thickness of 3.2mm, in accordance with BS EN 10210-1

The following types may not be used without design:

BS EN 39 type 3 steel tubes

Aluminium tubes

Other dimension, material or grade

26

Scaffold Boards

Platforms constructed from timber boards or decks of other materials

BS2482 Timber board (softwood) BS2482 Board (with nail plate option)

LVL Board (Laminated Veneer Lumber) Composite Plastic Board

27

Double Standards

New Text On Double Standards

May be required where additional ties or reduced bay lengths are not suitable.

Will have its own Base Plate. May not need to go to full height Secondary standard is connected to the

ledger.

28

Foundations

Loads newly available in Operational Guide to assist clients More foundation detail in Design Guide than before. Typical foundation design( leg) load is stated to be 19.7kN. Need for regular inspection of foundations.

Number of lifts

2 3 4 5 6 8

Foundation Load (kN)

10.5 11.8 13.1 14.4 15.7 16.4

( Load Class 4)

29

Structural Transoms

Structural Transoms are required for all TG20 Compliant Sheeted independent scaffolds, whether full or partly cladded and including some debris netted scaffolds.

30


Towers

31

Towers

Now three duty classes of tower: 0.75/1.5/2.0kN/m2 The eGuide provides a restricted range of external tower designs

which are dependent on a wind management system. Base dimensions now up to 2.7 x 2.7m No TG20 compliant designs are published for mobile towers

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Load Class

Maximum Load

Typical Uses

Minimum Bay Dimensions

Maximum Bay Dimensions

1 0.75kN/m2 Very Light Duty

1.2 x 1.2m 2.7 x 2.7m

2 1.5kN/m2 Light Duty

1.2 x 1.2m

2.1 x 2.1m

3 2.0kN/m2 Heavy Duty Towers

1.2 x 1.2m

1.8 x 1.8m

Stationary Free Standing Towers

33

Interior Access Birdcage Scaffolding


34

0.75

1.5

2.0

Interior Access Birdcage Scaffolding

Now 3 classes, not just 0.75Kn/m2

35

Highlighted need for foot lifts in single lift birdcages- stronger than in TG20:08

36

Tied Putlog Scaffolding


37

Free-standing Independent Scaffolding


38

Loading Bay


39

Loading Bays Revised dimensions, including 4.0m bay length. There are standard versions of 10kN and 15kN

loading Loading Bay Gates now included.

Loading Bays

40

Ladder Access Tower


41

Stairways Compliance to BSEN12811-1 Illustrated in Operations Manual

42

Chimney-stack Scaffolding


43

Compliant Scaffolding Features

Bridging with Beams

44

Bridging with Beams

Now allows for use of Aluminium Beams, as long as the same properties as the eGuide programme.

Includes 750mm deep beams TG20 Compliant bridges span 2 or 3 bays, dependent on which depth

of beam supporting ( nominally 305 or 610mm) Minimum structural properties of beams are in the Operational Guide,

Supports 10 boarded lifts with 1 inside board Supporting more lifts by repeating the bridge.

45

Beam Properties Steel or aluminium beams used within TG20 compliant scaffolds must comply with the minimum structural properties shown below:

Safe working moment resistance with 12.5 kNm Compression chord restraints at 1.2m spacing Safe working shear resistance 8.3kN Minimum ladder beam properties

Safe working moment resistance 27kNm With compression chord restraints at 1.2m spacing Safe working shear resistance 15.6kN Minimum unit beam properties

Prefabricated Beams

Structural property Minimum value

Structural property Minimum value

46


Prefabricated Transom Units

( Readylok / Bones )

48


Light duty protection fans

49


Pavement Lifts

Changed tie arrangements Max 2.7m pavement lift height Max 2.44m headroom

50

Lift Shaft Tower

51

Lift Shaft Tower

Maximum height 34m Loading 0.75kN/m2 on 2 lifts Maximum length 2.7m Securely butted in all 4 directions- no ties required.

52


Cantilevered Access Platforms

Should be at the same level as the main working platform

53

Temporary Roofs

Temporary Roofs are no longer covered by TG20, but by TG9

54

Hoardings More appropriately covered by TWF Hoarding Guide

Simplified Wind Classifications

Wind exposure affects the maximum height and tie duty, especially when sheeted or netted.

A simple wind exposure classification illustrated here is used with the TG20 Compliance Sheets (chapter 3)

A more accurate wind analysis is used in the TG20 eGuide, which can result in increased safe heights and reduced tie duties.

Further advice is provided for designers in TG20 Design Guide.

Wind exposure is classified as moderate, high or extreme

Other factors to be considered are site topography, seasonal variations and wind shielding in cities

Ties & Anchors

The Operational Guide now provides very extensive ( 30 pages ) guidance on this subject, not within the Technical Design Guide. The information seems to go further than the TG4 NASC guide.

Ties & Anchors

Plastic Plug

Self-Tapping eg Excalibur

T-Tie

Hilt-Type

Ties & Anchors

Tie details no longer in Technical Guide, but extensively in the Operations Guide

Importance of impermeable facades= TG20 Compliance

Permeable sheeted/ debris netted = designed

Additional Tie Load Class

Double proof-testing of nylon anchor positions if re-used.

Compliance sheets mainly based on 16m2 frequency.

Enforcement

TG20:08 to be officially withdrawn on

30th June 2014

There should be a bedding in period

TG20:13

Changes in TG 20 13

Documents

Transcript of Changes in TG 20 13