Identificantion of Key Elements

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Masts and Towers -standard nomenclatureguidance to theident i ficat ion an dreferencingJof key elements of mast andtower structuresThe contents of this Technical Bulletin are Advisory. The Bulletin is intended for use by .Project Sponsors, Properly Managers (PROMS),Establishment Works Consultants (EWCs),Works Services M anagers (WSMs), Project Managers and Consul tants engaged in theappraisal and inspect ion of Mast and Tower st ructures.Note: This Technical Bulletin (TB) is a reissue of TB 95/20 under a new issue num ber only.The contents of the TB 'have no t been updated for th is reissue, bu t wil l1 be reviewed in du ecourse.

SUBJECT CONTACT POINT:Wind Sensi t ive StrucluresSpec ia l i s l ServicesSutton Coldfield Mi l Extn2174Di rect D ia l l i ng 0121 311 2174

DEFENCE ESTATESMINISTRY O i DEFENCEJuly 2000

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Masts and Towers - standard nomenclatureguidance to the ldentlfication andreferencingof key elements of mast andtower structuresMasts and Towers - standardnomenclature guidance to theidentification and referencing of keyelements of mast and tower structuresINTRODUCTlON1. This T echnical Bullet in explains the DE Stand ard Nom enclature System forthe referencing and namin g of key locations and p arts of a Mast or Tower.2. Th e conte nts of the B ulletin are advisory and should not be interpreted as

an instruction to carry out any works.Works undertaken on a M ast or Tower will almost certain ly require specificlocations on the stru ctur e to be referenced. Witho ut a common syste m thiscan be difficult and inefficient to achieve and therefore th e pote ntial for

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confusion and possible error exists. I4. There is no universally adopted M asts and Tow ers nomen clature system.Various org anisatio ns have, to differing degrees, adopted their own sy stem swhich they use on a unilateral basis.

This Bullet in descr ibes the DE System recommended for use within MOD.I t is recommended t ha t the system is automatically ad opted for all newstructures and introduced into exist ing structures by Property Man agers ona n opportunity basis, ie at the next m aintenance inspection or app raisal .

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DESCRIPTION OF MAST AND TOWER TYPES6.

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To assist w ith th e definitions of thestruc ture s covered by this Bulletin,se t out below are th e category typesof masts and towers and the i rdescriptions to aid with th eiridentification.Se l f Sum or t in e S tee l Towers.Stru cture s which can be groupedunder this descr iptionare al lf ree-standing having al l structuralmembers made from steel. Theywill not be relia nt on any externalstr ut s or t ies for their support .Refer to Fig 1.1The steel mem bers may be made fromstan dard or fabricated sections of any type,including circular hollow tub e, hot rolledopen sections and circular solid sections .

Fig 1.1 A typical self supporting sreel rower1


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Masts and Towers -stan dard nomenclatureguidance to the identification andreferencing of key elements of mas t andtower structures

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Steel towers a re built to suit the requirements of the duty to be performedbut the majority of structures are either square or triangular in plan, usingfour o r three main legs respectively. Where the structure is triangular inplan the use of circular leg sections is most common.In elevation a wide variety of shapes a re employed to suit the circumstances,parallel sided, straight tapered and eiffelised.These structures will be used to support equipment of all types, such asmicrowave dishes, floodlights, radar installations, sirens, UHF and VHFaerials. Their heights will vary from say 2 or 3 metres where they are usedas mounting supports fitted to the roofs of buildings, up to 150metresfounded at ground level, with the majority falling into the range of 15 to 50metres.Self Suooortinrr Timber Towers. The majorityof this group of structures were built circa1930/1940s. he struc tural members of thesetowers were made entirely in timber usinggalvanised steel bolts and leg splice angles orplates a t the joints. All timber towers are selfsupporting and do not rely on any externalstru ts or ties as part of the support mechanism.An illustration of such tower is given in Fig1.2.Due to the nature of the material, timber iscut into square or rectangular sections. Thesectional shape does not lend itself toconnections other than at right angles; Hencethere are no triangulartimber towers; all are square in plan.The majority of timber towers are straightsided and tapered, but there are a very fewstructures which are eiffelised in elevation.

Fig 1.2 A typical self suppolting l imber towerTimber towers have been constructed to heightsof up t o 73 metres, but the majority ofstructures are between 15 o 40metres.-elf Sueoortine Hvbrid Steel and Timber Towers. To all outwardappearance this relatively new group of structures looks little different toother towers. The timber section of the tower usually forms the upper thirdof the structure, where Tx and Rx antennas are fitted. Access ladders andplatforms within the timber section are also constructed using non metallicmaterials wherever possible.This hybrid tower has evolved as an economical solution to the requirementof the Equipment Sponsor to only have non conductive materials adjacent tothe antenna equipment.Guved Masts and Poles. All of these structures consist of a vertical mast OTpole element, held in place with guy or stay wires.The base is normally pinned. The vertical element may be formed usingsteel or aluminium lattice construction, usually incorporating climbing rungsintegral with the structure or as a tube with bosuns chair access. Thesetypes are referred to as guyed masts. Refer to Fig 1.3.

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Masts and low er s -standard nomenclatureguidance to the identification andreferencing of ke y elements of mast andtower structures

20. The plan section of lattice masts can be either triangu lar or square, with theformer being most common.21. Guyed poles are formed using a vertical element constructed in steel,aluminium ,glass re-inforced plastic (GRP) circular hollow section, or solidtimber ( telegraph poles). The poles are usually pinned except for the solidtimber which is cast in at the base or in a tabernacle and sometimessteadied using stays. A typical guyed pole is illust rated in Fig. 1.4

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Fi g 1.3 A typical guyed mast Fig 1.4 A typical guyed poleThe most distinguishing features of this group are the guys, or stays , whichare attached to the mast, or pole, and anchored at t heir lower ends todiscrete foundations. The configuration of the guys will be determined bythe design of the structure, but t he most common plan arrangement is toprovide th ree equally spaced s ets of guy lanes, although some arrangementsprovide four sets .Principally guys a re constructed from the following :-

a Galvanised steela Plastic impregnated steelStainless steel'Parafil' (or similar)Prestretched Polypropylene I

Termination of the guy ropes a t the lower end will include a length variationmechanism to allow tensions to be adjusted from time to time. This isusually a turnbuckle with a length of chain for coarse adjustment.A t po un d level, the anchors on which the guys are terminated are usuallyconstructed in concrete. Climbing access up the mast can be built into thelattice framework. Access u p poles is often by a bosuns chair attachedthrough a pulley block mounted at the mast head.

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Masts and Towers - standard nomenclatureguidance to the ide ntification andreferencing of ke y elements of mast andtower structures

26 . The guyed masts in the MOD Estate usually do not exceed 50 metres tal l ,but the re are a small number which are u p to 274metres tal l . This guide isintended to incorporate the procedures to be adopted for all guyed m ast s upto 150metres. Taller masts should be taken as a special case.STANDARD NOME NCLATURE FOR MASTS AND TOWERS21 .

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The following guidance notes describe the g eneral rul es for esta blish ing astandard nomenclature system for numberingflet tering the main elemen ts ofMa sts and Towers. Specific examp les are given and included indiagrammatic form.General . Where given, directions are relevant to th e planviewed from the top.Legs a re designated by let ters A,B or C fortr iangular structures and A,B,C or D or squarestructures.

A430. Faces are designated by a number 1,2 r 3 or 0t r iangular towers and 1,2,3 r 4 or square towers.Face 1 s the face between legs A and B and face 2between legs B and C etc.

EFi g 1 S l o w e r eg B face designations

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31. Towers Where the designatedrou te of access is a leg (step boor ladder at tach ed central to theleg and external to the tower) ,the leg is designated" leg A . S e e F i g 1.6.B2 C 2

Fig 1.6 Le g Designation

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Masts and lowe rs - standard nomenclatureguidance to the identificatlon andreferencing of key elements of mast andtower structures

32. Where the design ated route of accessis awa y from a leg "leg A ' isdeterm ined as follows:A

a . For towers with externalaccess the climber st and s facingthe d esignated method of accessas if to climb. The leg to hisright is "leg A . See Fig 1.7

C 2

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b. For towers with in tern al access,the climber stan ds facing theaccess rou te a s if to climb.He then , whilst still facing theaccess route, moves back un til heis standin g imm ediately outsidethe tower. The leg to his right is"leg A unless there is then a legimm ediately in front of him, inwhich case th at is leg A. See Fig 1.8:

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Fin 1.7 External access systems IA

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Typical configurations of inte rnal an d 1external mou nted access systems forsquare and tr iang ular towers areshown in Figs 1.6, 1.7 an d 1.8.C E 2 B

Fip 1.8 Internal access systems

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Masts and Towers - standard nomenclatureguidance to the identification andreferencing of ke y elements of mast andtower structures

34 . Towers are comm only constructed in p anels. An elevation of a typicaltower showing panel numbering is shown in Fig 1.9.

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Fig 1.9 Elevation Typical Tower (Panel numb ering indicative only)

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Masts and Towers - standard nomenclatureguidance to the identification an dreferencing of ke y elements oi mast andtower structures

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39. Where t..ere is no des igna ted access sys tem ,e.g. on a cylindrical mast, the followingapproach is to be adopted, see Fig 1.11:a. I f one stay lane performs a dominant

"bac kstay" function i.e. it direc tly opposesone or more directional ant enn a take-offloads, then this la ne shall be defined as"lane A .If a. above is not applicable and ther e is a. lane with spe cial or additional ancho rage C lfor lowering the s t ructu re, then th is lane shal lbe defined as "lane A'.

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A IPSCL rn 1Ac. If neith er a. nor b. s applicable, lanedesignation may be selected appropriate tothe s i te. tl

Fi g 1.11 Cylindrical masts with no designated access System

Guy levels a re numbered sequential lyfrom the groun d upwa rds with the lowestguy take-off po int being "level l " , seeFig 1.12.Th e complete designation for a guyincludes lane and level as follows:GUY : LANE B : LEVEL 1 B1)Anchor blocks shall be deeignated bya lane and "anchor" position.Anchor blocks are numbe redradiat ing outwards from theillustrated in Fig 1.12.The com plete designation for anblock includes the la ne lette r annumber as follows:ANCHOR : L A N E C : ANCH(C2)

, M ,

wwc m a a , U a a I

Fig 1.12 Elevalion typical guyed mast


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Masts and Towers - standard nomenclatureguidance to the identification andreferencing of key elements of mast andtower structures

45 . In som e instances a dual guy systemmay be encountered a t var ious levels.Th e two guy wires are identified bys tanding a t the back of the anchorposit ion ( looking a t the ma st) anddesignating the lef t hand side (LHS)and r ight hand side (RHS).46. The complete designation for dua lguys includes lane, level and side asfollows:GU Y :LANE C : LEVEL RHS

Most

Fig 1.13 Plan View of dual guy Designation

47 . An tenn a Blocks. Anchor blocks provided solely for back stays for anten na ssupplem entary to th e pr imary stay s shall be numbered as "anten na block"and num bered sequential ly star t in g from A.48. Top antenn a radial elements performing a dua l structura l and op erationalrole us e lan e designation A,%$ etc. Lane A being coincident or ne xtclockwise position from lane A stay s below (wh ere applicable). See Fig 1.13

A1A TOP RnDIALS/SlAYS

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Fi n 1.13 Se e note 48


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Masts and Towers - standard nomenclatureguidance to th e identification an dreferencing of key elements of mast andtower structures

CONCLUSION49. The majority of mast and tower structures found on the MOD state will beable to have their key elements identified by using the standardnomenclacture system explained and depicted above.50. There will be instances where the structure and its associated elements willdiffer from those shown in this Technical Bulletin. If a standardnomenclacture cannot be designated for the structure, then furtherassistance can be sought from the subject contact point as given at the frontof this TB.

RECOMMENDATIONSI51. Once the agreed nomenclature for any one structure has been established I tshould be clearly indicated on the structure and recorded in the property file.52. Markings on the structures should be as follows:53. Masts. All designated guy anchors should be identified by marking theupper surface of the concrete anchor with black paint using a stencil with aminimum letter height of 150mm.

The stencil should be positioned so that the marking may be read easilywhen walking around the anchor position. See Fig 1.14.54. Designated anchor block positions should also be marked in a similar

fashion adjacent to or under the landanchor marking (see note 39 and 40).

Fig 1.14 Guyanchor marking55 . Where masts have no visible anchor blocks (buried dead man anchor) thedesignated guy lane and position should be identified by securely attaching asuitable label to the guy terminations and marking the designation with anindelible marker.

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Masts and Towers -standa rd nomenclatureguidance to the identification andreferencing of key elements of mast andtower structures

56. Steel Towers. All designated legs should be identified by ma rkin g the legsection surface with black pai nt via a stencil.Th e size of stencil to us e will be dependent on the size and type of leg to bemarked. Posit ion of the m arking should be approximately 1.5m aboveground level and should face outwa rd on the tower face.

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57. Timber Towers. Paintin g of t imber sections is not advisable. Thedesignated leg should be marked via a brass plateAetter secured with 50m mlong brass screws. If vandalism and th eft is considered to be a problem theposit ion of any brass le t ters should be a t a minimum height of 2.5m boveground level. The lett ers should face outward s from the tower face.55. Records in the property files are recommended to be in the form of a l inediagram drawing. Example drawings for a mast an d a tower are shown inFigs 1.15 and 1.16 respectively.

Bulletin Authorised Bv:-

J LAWLORHead Specialist ServicesI

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Masts and Towers - standard nomenclatureguidance to the identification andreferencing of key elements of mast an dtower structures

Prepared By : Slructure Reference:Location:

PANEL

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Dale:Drg No:

Fig 1.15 Typical lower line diagram

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Masts and lower s - standard nomenclatureguidance to the identiflcation andreferencing of key elements of mast andtower structures

Skri rh rmrndolia Drlailr if KnownPrepared By: S l r u c l u r e Reference:1 Location: Dale:D rg No:

Fi g 1.16 Typical mast line diagram

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Identificantion of Key Elements

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