communication structures
TRANSCRIPT
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Communicationstructures
Brian W. Smith
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Published by Thomas Telford Publishing, Thomas Telford Ltd, 1 Heron Quay, London E14 4JD.www.thomastelford.com
Distributors for Thomas Telford books areUSA: ASCE Press, 1801 Alexander Bell Drive, Reston, VA 20191-4400
Japan: Maruzen Co. Ltd, Book Department, 3—10 Nihonbashi 2-chome, Chuo-ku, Tokyo 103 Australia: DA Books and Journals, 648 Whitehorse Road, Mitcham 3132, Victoria
First published 2007
A catalogue record for this book is available from the British Library
ISBN: 978-0-7277-3400-6# Brian W. Smith 2006
All rights, including translation, reserved. Except as permitted by the Copyright, Designs andPatents Act 1988, no part of this publication may be reproduced, stored in a retrieval system ortransmitted in any form or by any means, electronic, mechanical, photocopying or otherwise,without the prior written permission of the Publishing Director, Thomas Telford Publishing,Thomas Telford Ltd, 1 Heron Quay, London E14 4JD.
This book is published on the understanding that the author is solely responsible for the statementsmade and opinions expressed in it and that its publication does not necessarily imply that suchstatements and/or opinions are or reect the views or opinions of the publishers. While everyeffort has been made to ensure that the statements made and the opinions expressed in thispublication provide a safe and accurate guide, no liability or responsibility can be accepted in
this respect by the author or publishers.
Typeset by Academic þ Technical, BristolPrinted and bound in Great Britain by MPG Books, Bodmin, Cornwall
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Contents
Foreword
Preface xi
Acknowledgements xiii
Chapter 1 Introduction 1
Chapter 2 History 6
Chapter 3 Design considerations 193.1 General, 193.2 Choice of site, 203.3 Choice of structure, 243.4 Economic considerations, 273.5 Environmental considerations, 273.6 Electronic considerations, 30
3.6.1 General, 303.6.2 Antenna characteristics, 333.6.3 Low-frequency antennas, 373.6.4 Medium-frequency antenna systems, 413.6.5 VHF and UHF antennas, 443.6.6 Digital audio broadcasting, 493.6.7 Mobile phone antennas, 513.7 Effect on existing services of subsequent additional
antennas, 54
Chapter 4 Failures of masts and towers 564.1 General, 56
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4.2 Icing failures, 594.3 Design/detail failures, 614.4 Maintenance failures, 634.5 Aircraft damage, 654.6 Vandal damage, 684.7 Lessons to be learned, 69
Chapter 5 Forms of structure 715.1 General, 715.2 Timber towers, 715.3 Concrete towers, 715.4 Lattice steel towers, 75
5.5 Lattice guyed masts, 815.6 Tubular guyed masts, 875.7 Concrete guyed masts, 905.8 Other forms of communication structures, 91
Chapter 6 Meteorological parameters 936.1 General, 936.2 Wind, 936.2.1 Wind climate, 956.2.2 Boundary layer, 996.2.3 Serviceability wind speeds, 1026.3 Atmospheric icing, 1046.3.1 General, 1046.3.2 Physics and theoretical modelling of ice accretion, 1076.3.3 Empirical models to estimate ice loads on
structures, 1096.4 Earthquakes, 1136.5 Temperature, 1146.6 Other meteorological aspects, 115
Chapter 7 Wind resistance 1177.1 General, 1177.2 Symmetrical structures without ancillaries, 1227.3 Symmetrical structures with limited ancillaries, 1287.4 General method for structures containing
ancillaries, 129
7.5 Linear ancillaries, 1337.6 Discrete ancillaries, 1337.7 Cables, 133
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7.8 Measurements on scale model of communicationstower, 134
7.9 Discrepancy between wind tunnel tests and full-scalemeasurements, 137
7.10 Icing, 140
Chapter 8 Response 1478.1 General, 1478.2 Lattice towers, 1488.3 Guyed masts, 1508.3.1 General, 1508.3.2 Frequency domain analysis, 152
8.3.3 Time domain analysis, 1578.3.4 Simplied methods, 1598.3.5 Summary, 176
Chapter 9 Strength 1779.1 Introduction, 1779.2 Design against buckling — individual members, 1789.2.1 General, 1789.2.2 Inuence of local and torsional buckling, 1809.2.3 Angle leg members, 1819.2.4 Angle bracing members, 1829.2.5 Tubular leg members, 1849.2.6 Tubular bracing members, 1849.2.7 Solid round members, 1849.3 Secondary members (‘redundants’), 1859.4 Bracing types, 1869.5 Compound members, 1899.6 Tension, 1909.7 Connections, 1909.7.1 General, 1909.7.2 Flange joints in tubular or solid round leg
members, 1909.7.3 Guy connections, 192
Chapter 10 Cables 19510.1 General, 195
10.2 Types of cables, 19510.3 Strength of guy ropes, 20210.4 Rotational characteristics of steel ropes, 202
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10.5 Modulus of elasticity, 20310.6 Prestretching, 20310.7 Still air tension, 20610.8 Terminations, 20610.8.1 General, 20610.8.2 Types of terminations, 207
Chapter 11 Aerodynamic stability 21011.1 General, 21011.2 Vortex shedding, 21111.2.1 General, 21111.2.2 Background and critical wind speed, 211
11.2.3 Practical implications, 21311.2.4 Damping devices, 21411.3 Galloping, 21611.3.1 General, 21611.3.2 Critical wind speed, 21611.3.3 Damping devices, 219
Chapter 12 Fatigue 22012.1 General, 22012.2 Lattice towers, 22312.3 Lattice masts, 22312.4 Guys, 226
Chapter 13 Foundations 22813.1 General, 22813.2 Foundation types, 22813.2.1 Type I: to resist uplift, 22813.2.2 Type II: to resist overturning, 23113.2.3 Type III: to resist down thrust, 23313.2.4 Type IV: guy anchorages, 233
Chapter 14 Codes and standards 23914.1 History, 23914.1.1 General, 23914.1.2 Wind loading, 23914.1.3 Ice loading, 242
14.1.4 Strength, 24314.1.5 Other aspects, 24314.2 Current codes, 244
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14.2.1 General, 24414.2.2 Comparison of current Codes, 245
Chapter 15 Access and safety 24615.1 General, 24615.2 IASS Recommendations for safe access, 249
Chapter 16 Fabrication and erection 25116.1 Materials and fabrication, 25116.1.1 Steel for towers and mast columns, 25116.1.2 Aluminium, 25716.1.3 Timber, 257
16.1.4 Plastics, 25816.2 Erection, 25816.2.1 General, 25816.2.2 Erection of lattice towers, 25916.2.3 Erection of guyed masts, 259
Chapter 17 Maintenance 26417.1 General, 26417.2 Constraints, 26417.3 Minimizing maintenance at the design stage, 26517.4 Manuals, 267
Chapter 18 Seismic response 26918.1 General, 26918.2 Seismicity and earthquake-resistance performance levels, 27018.3 Prediction of seismic response of structures, 27118.3.1 General, 27118.3.2 Self-supporting lattice towers, 27218.3.3 Monopoles, 27318.3.4 Guyed masts, 27318.3.5 Antennas and ancillary components, 27518.4 Geotechnical considerations, 275
Annex A Codes of Practice and Design Standards 276A.1 General, 276A.2 Comparisons of National Codes, 277
A.3 Scope, 277A.4 Limit states/reliability classes, 277A.5 Wind structure, 279
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A.5.1 General, 279A.5.2 Wind resistance, 286A.6 Ice loading, 292A.7 Displacements/serviceability, 293A.8 Partial safety factors, 295A.9 Strength, 298A.9.1 Compressive strength, 298A.9.2 Tensile strength, 303A.9.2.1 Steel structure, 303A.9.2.2 Guys, 303A.10 Guy assemblies, 304A.10.1 General, 304
A.10.2 Prestretching, 304A.10.3 Terminations, 304A.10.4 Initial tensions, 305A.11 Erection, 305A.12 Insulators, 305A.13 Access, 307
Annex B IASS Working Group Number 4: Masts andTowers 308
B.1 Brief history, 308B.2 Role in the future, 308B.3 The members of the Group, 309
References 311
Index 327
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Foreword
Today none of us can enjoy modern life even for a single day withoutmaintaining communication with others or receiving informationfrom radio and TV. Nevertheless, very few of us recognize that thesemodern conveniences are literally supported by structures properlydesigned, constructed and maintained for that particular purpose.
Although some of the tasks of terrestrial antennas have been takenover by celestial ones, more and more demands for transmission struc-tures for local and ground communication have emerged in recent years. In Japan, for instance, the meteorological radar station on topof Mount Fuji, which had served for 35 years for weather forecasting,was dismantled and replaced by satellites in 1999. Meanwhile, thedemand for a new Tokyo Tower for the ground digital communicationnetworks, which may be twice as tall as the existing one, is now underdiscussion. A remarkably high structure like a TV tower often incorpo-rates a viewing platform or restaurant for people at its top, and plays animportant role as a tourist centre in the locality, too.
Brian Smith’s book on communication structures is a thorough studyof the technology of structures supporting communication systems forour society. It covers a very wide range of tower and mast structures,and looks at them from their history, forms, loads, analysis anddesign, codes and standards, fabrication and erection to their mainte-nance. The book also deals with access and safety of masts andtowers, part of which has already been published within the IASS(International Association for Shell & Spatial Structures). I am surethat engineers who are working in the elds of design, analysis, fabrica-
tion and construction of masts and/or towers will accomplish their taskswith condence by making good consultation with the book, which alsocontains comprehensive references for further study.
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Brian Smith and I have been good friends for more than fteen years,mainly through activities in the IASS. He has been a member of theIASS for a long time, and is currently one of the most activemembers of the IASS Executive Council. In 1997 he was conferredthe IASS Tsuboi Award for his excellent joint paper on ‘SimpliedDynamic analysis Methods for Guyed masts in Turbulent Winds’presented in the IASS Journal.
The IASS Working Group 4 for Masts and Towers, in which Brianhas played the leading role, is the most animated working group inthe Association. According to Brian he has received a great deal of help and advice from members of Working Group 4. On behalf of theIASS I am very proud of the Working Group as well as Brian himself,
and would like to congratulate the Working Group and all the consti-tuent members of the Group on the publication of this remarkable book.
Mamoru Kawaguchi, President of IASS, June, 2006
In preparing the report for the Executive Council meeting held in Mont-pellier, France on September 19, 2004, I was informed by Ulrik Støttrup-Andersen, Chairman of IASS Working Group 4 on Masts and Towers,
that Brian Smith has, with the support of WG4, agreed to write a bookon communication structures, and that IASS WG4 will act as the‘backing group’. By having the research results published in the form of a book, available in libraries and/or bookshelves is the highest statusthat can be achieved by an IASS working group and its members.
The importance of communication structures cannot be underesti-mated, as the failure of communication facilities can sometimes bequite destructive. One example was the malfunction of the communi-cation facilities of a key station in the Kobe area of Japan immediately
after the January 17, 1995 earthquake. This event was said to haveprevented local governments knowing the level and scope of casualtiescaused by the disaster; as we know, this is crucial for the rescue of injured people from collapsed buildings in the rst few critical hours.
On behalf of the IASS Technical Activities Committee, I would liketo congratulate Brian for his endeavor in making this book a reality, andWG4 for their backing of such an endeavor. We believe that with thisbook, engineers and researchers working on communication structuresand the like can benet greatly from the huge amount of informationprovided.
Y.B. Yang, Chair, Technical Activities Committee, IASS. Taipei, Taiwan
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Preface
Communication structures, in the modern sense — masts and towers — arenow familiar to everybody as these structures are situated in the openlandscape as well as in the middle of our cities. The tall masts andtowers for broadcasting of radio and TV have gradually been acceptedby the public, and now their focus is on the numerous number of smaller masts, towers and poles primarily used for mobile networks.
However, most of the general public are unaware of the engineeringchallenges and specialisms behind these common structures. They arenot aware that ‘a guyed-mast is one of the most complicated structuresan engineer may be faced with’ when driving by in their cars they see a300m broadcast mast; and nobody worries or gets nervous when theysee on their TV screens the message ‘temporary deterioration of thesignal due to icing of the Emley Moor antenna’. It is of course wrongto say ‘nobody’ because there is a group of people — structural engineers,scientic researchers, mast and tower owners, antenna experts etc.,which know and ‘worry’. This group, heavily involved in the analysis,
design, construction and operation of communication structures,have for a long time been discussing new developments, exchangingexperiences, launching new designs, presenting numerous technicalpapers etc. worldwide, but have not until now systematically accumu-lated or gathered their knowledge into one work. This has led to asituation where analysis and design of communication structures hasnot appeared as part of the syllabus for structual engineers at technicalunversities; and young engineers starting on their professional careerhave had no introduction to this eld other than the experienced
personnel in a company.With this book, Brian W. Smith has covered the subject very
effectively indeed; and this title will surely be invaluable not only for
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the new generation of engineers — whether they study at technicaluniversities or they start their professional carreer in engineering prac-tices, telecom organisations, with contractors or mast and tower fabri-cators, but also certainly for the established mast and tower experts.Communication structures is the rst work of its kind, which in aninstructive and clear way expounds the background of communicationstructures, taking into account all the issues involved in the analysis,design, fabrication, construction and maintenance. It is fully illustratedwith excellent photographs and gures throughout and makes referencesto actual real-life constructions.
Brian W. Smith has been involved in the analysis and design of communication structures all of his professional life as a partner of
Flint & Neill Partnership. He has been involved as the expert in allthe British codes and standards directly related to masts and towers,and for those with inuence on masts and towers. Internationally,Brian has been a very active member of the IASS (InternationalAssociation for Shell and Spatial Structures) Working Group for Mastsand Towers since its formation in 1969, and for ten years he waschairman of the group. Perhaps, most signicant, is Brian’s inuenceon the new common Eurocode for Towers and Masts, a work he haschaired and steered from its inception in 1993 to the nal draft whichwas accepted unanimously by all the European states in 2003.
So when Brian gives credit for the book to the IASS WG 4 — it is forall members of this Group a great honour — an honour that none of usreally deserve.
Ulrik Støttrup-Andersen, Chairman of IASS Working Group No. 4
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Acknowledgements
The author has received a great deal of help and advice during thepreparation of this manuscript. Working Group 4 (WG4) of the Inter-national Association of Shell and Spatial Structures (IASS) hasprovided both much of the source material as well as support for thisventure. In particular, the following members of IASS WG4 haveprovided both advice and technical input to certain chapters asbelow:
Ondrej Fischer (Chapter 11)Duncan Gould (Chapters 3, 7, 9, 13, 16 and Annex A)Mark Grant (Chapter 15)Tony di Guglielmo (Chapter 3)Peter Heslop (Chapters 2, 3)Mark Malouf (Chapter 14 and Annex A)Don Marshall (Chapter 16)Ciro Martoni (Chapter 10)Ghyslaine McClure (Chapter 18) John Mearns (Chapters 3, 16, 17)
Miros Pirner (Chapter 7)Bruce Sparling (Chapter 8) John Wahba (Chapter 14 and Annex A)Simon Weisman (Chapters 4, 5, 7, 8)Geoff Wiskin (Chapters 2, 3, 4)
In addition Ulrik Støttrup-Andersen (Chairman of IASS WG4) and
Mogens Nielsen (Secretary of IASS WG4) reviewed and made valuablecomments on all chapters. A full list of the current active members of IASS WG4 is given in Annex B.
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Material which appears in Chapters 18 and Annex A is reproducedwith the permission of Canadian Standards Association. Material isreproduced from CSA Standard CSA-537-01 Antennas, Towers andAntenna Supporting Structures, which is copyrighted by CanadaStandards Association, 178 Rexdale Blvd, Toronto, Ontario,M9W 1R3, www.csa.ca. While use of this material has been authorized,CSA shall not be responsible for the manner in which the information ispresented, nor for any interpretations thereof.
Permission to reproduce extracts from BS 8100-4: 1995 is granted byBSI British Standards and can be obtained from BSI Customer Services,389 Chiswick High Road, London W4 4AL. Tel: þ 44 (0)208996 9001.email: [email protected]
The support of the IASS through the President, Professor MamoruKawaguchi, and the Working Bureau is most gratefully acknowledged.Finally, I would like to thank Flint & Neill Partnership for allowing
me to prepare this document with their support, for my colleaguesDavid MacKenzie and John Rees for reviewing the draft and providingvaluable comments, and to Helen Cartwright for patiently typing themanuscript.
All gures are reproduced with the kind permission of Flint & NeillPartnership unless otherwise accredited.
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3Design considerations
3.1 GeneralFrequently the design and construction of the antenna supportstructure is, in terms of costs, a relatively small element in a complexproject comprising access roads, buildings, site development, trans-mitters, monitoring equipment, power supplies, antennas and feeders.The project management team will need experts in each of thesedisciplines. However, the specication for each discipline is oftenproduced independently, in spite of the inter-relationships with otherdisciplines. Generally the fundamental parameters are the availablefrequency at which the signal is transmitted, and the proposedservice area (the population targeted to receive the service). A‘service area plan’ is then developed, which explores available sites,the height of structure needed and the radiated power necessary todeliver the signal. This proposed radiated power, in turn, denes theoptions for the physical size and disposition of the antenna andfeeders, which in their turn dene the weights and wind resistance to
be carried by the structure. These data are then incorporated intothe design brief and passed to the structural engineer.Frequently the structural engineer is unaware of possible alternatives
that may provide the client with a more economical solution. Forexample, in broadcasting the transmitted signal strength or effectiveradiated power (erp) is a function of the transmitter power and the gainof the antenna array. By increasing the transmitter power the gain (andthus the length of the antenna aperture) can be reduced, savingantenna cost and signicantly reducing the structural loading. Unfortu-
nately this increases the initial cost of the transmitters and also thepower consumption and running costs. Broadcast project engineershence have to try to optimize the combination of transmitter and
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antenna costs but, unless they are alerted by the structural designer, rarelyconsider the potential reduction in structure cost which a smaller antennamight permit. For example, a slight reduction in antenna loading mightallow a standard ‘off-the-shelf ’ structure to be used rather than a morecostly ‘special’ design. More commonly on existing structures, a smallerantenna may be possible without the need for structural strengtheningwhereas a larger antenna could necessitate signicant strengthening.
3.2 Choice of siteThe selection of the site must take into account:
. The area to be served by the installation; clearly this is dependent onthe type of service to be provided — cellular phone, television, micro-wave networks, etc. — and on the density of population in that area.This will have economic and environmental implications.
. The distribution of the population in that area; this could affectthe directionality needed of the antenna system and, possibly, theorientation in plan of the structure itself (see section 3.6).
. The general nature of the terrain; this will affect the height of thestructure (see below).
.
The presence, or otherwise, of high ground in the locality; this canagain alter the height of the structure, and the viability of sites in theshadow of the high ground.
. The radiation pattern from the proposed antenna; for example forTV broadcasting whether the horizontal pattern of radiationshould be omnidirectional or shaped to provide increased powertowards more distant parts of the served area. On occasions thepattern needs to be shaped to protect an adjacent service on thesame frequency.
. For telecommunication structures used for mobile phone services,the principal concern is the aesthetics of the structures, particularlyin suburban areas. Novel lattice structures are often needed toplacate local Authority demands and residents’ concerns (seesection 3.5).
The nal choice is invariably a compromise between economics of the proposed service and the demands of other services in differentfrequency bands that could enable co-siting to be considered.
The range of a broadcast signal, and hence the service area covered, isgoverned not only by the erp from the antenna but also by a combinationof the height of the antenna and the nature of the terrain and the
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broadcast frequency. The higher the broadcast frequency the more theservice area will be restricted to line of sight from the antenna.
For TV and FM radio the height of the antenna above the meanground between the transmitter and receiver is a crucial factor in deter-mining the strength of the signal received. This height depends partlyon the elevation of the chosen site, and partly on the height of theantenna above the site ground level. Generally speaking, high supportsare required when the terrain is level (effective site height small) (seeFig. 3.1(a)), and in such cases conditions will normally favour the erec-tion of high structures, whereas in mountainous regions, where theelevation of the site is signicant but erection conditions difcult,lower supports can be used (see Fig. 3.1(b)). This is well illustratedby comparing Denmark and the Netherlands where mean site eleva-tions are practically zero and antenna structures over 250 m high arecommon, with Spain and Portugal where sites often exceed 500 m inelevation and the average structure is some 60 m high.
The broadcast frequency also has a signicant inuence on the rangeof the signal. Lower frequency signals have greater ability to diffractaround obstructions and hence the amount of shadowing from a xed
source increases rapidly with frequency (see Fig. 3.2).Ideally, however, the transmitting site should provide an unobstructed
line-of-sight over the area to be covered, particularly for UHF services.
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Coverage
(a)
Same coverage as for level terrain, using shorter structure
(b)
Fig. 3.1 Aerial coverage
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Index
Page numbers in italics refer to diagrams and illustrations.
accesscodes and standards 307denition 247safety 33
climb duration 247climber competency 250guidelines 246ÿ 247ladder types 249
system sophistication 248aerodynamic responses see galloping;
vortex sheddingaesthetics 2
cellular phone antennas 52, 54, 92, 92
aircraftdamage to guyed masts 65 ÿ 66, 66 , 67 ,
68mast warning lights 66, 265painted warnings 265
altitude, and wind speeds 282 ÿ 284, 283aluminium, uses of 257angle leg members
angle bracing 182ÿ 183eccentricities 183
compound cruciform bracingbolted 182, 182
welded 182, 182
symmetric bracing 181, 181
unsymmetric bracing 181 ÿ 182, 181
angled sections, buckling curves178ÿ 180, 178 , 179
antenna aperture, denition 44
antennassee also masts and antennas by typeband specic 78digital audio broadcasting 49 ÿ 51gain 44ÿ 45interference between 54 ÿ 55low-frequency systems 37ÿ 41, 39
medium-frequency systems 41 ÿ 44, 42 ,43
multi-purpose, compromises 26 ÿ 27,33ÿ 34
radiation patternshorizontal 35 ÿ 37, 37 , 38 , 44vertical 34 ÿ 35, 35 , 36
seismic responses 275tilt/height effect 34, 35
VHF/UHF systems 44 ÿ 49, 45 ÿ 49
Australiacodes and standards 276, 292
reliability classes 280
Batsfjord cylindrical mast (Norway) 88bending moment responses, guyed masts
165, 165
Berlin Tower (Germany) 72bi-metallic corrosion 266bolts, yield strength 257boundary layer, wind climates 99
bracing systems 299see also connectionscompound members 189 ÿ 190, 189
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bracing systems (continued )cross-bracing 186ÿ 187, 186
with horizontals at centreintersections 186 , 187ÿ 188
with redundants 186 , 187K 188, 188
cranked 188 ÿ 189, 188
multiple lattice 188 , 189portal frame 188 , 189single lattice 186, 186
tension 186 , 187in tension 190
British Broadcasting Corporation (BBC),wind loading curves 239 ÿ 240, 240
broadcast frequencyidentifying 19signal range 21ÿ 23, 22
broadcastsearly
France 12UK 13ÿ 14
future developments 18Marconi’s experiments 12 ÿ 13
bucklingcurves, angle sections 178 ÿ 180, 178 ,
179local and torsional 178 , 180ÿ 181
building mounted lattice towers, seismicresponses 272
Canadacodes and standards 276
reliability classes 280cantilevers
guyed mastserection 263guy tensions 174, 175
patch load analysis 170 ÿ 171lattice steel towers 86
capacitance discs, low-frequencyantennas 41
cellular phonesantennas 27, 52, 53 , 54, 54
aesthetics 52, 54, 92, 92
design objectives 92
disguised as trees 30, 30rst generation systems 51 ÿ 52second generation systems 52
services 18third generation systems 52
Charpy V-notch tests, normalization 252252
clamped terminations, guy cables 198climber competency, and access safety
250CN Tower Toronto (Canada) 72, 73
lightning strikes 115 , 116codes and standards
access 307Australia 276Canada 276, 279comparisons 277, 278deection angles 295drag coefcients 286 ÿ 287, 288 ÿ 291 ,
292erection tolerances 305, 306Eurocode 3 244, 276, 279, 282Germany 244guy assemblies 303ÿ 305guyed masts 279
deection limits 243 ÿ 244ice loadings 242, 292insulators 305 ÿ 306lattice steel towers 279national 3partial safety factors 295ÿ 298reliability classes 280ÿ 281serviceability factors 293ÿ 295, 294
strength 243compressive 298, 300 ÿ 303tensile 303 ÿ 304
UK 245, 276USA 244, 276, 279wind loadings, early 239ÿ 242, 240 , 241wind speeds
and altitude 282 ÿ 284, 283
and gust speeds 282
and topography 283 ÿ 284, 284 , 285 ,286
wind structures 279, 282 ÿ 284, 285 ,286
collapses see failurescommunication towers, environmental
impact 28 ÿ 29, 29compound members, bracing systems
189ÿ 190, 189
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compression strengthsangle leg members
angle bracing 182ÿ 183compound cruciform bracing 182,
182
symmetric bracing 181, 181
unsymmetric bracing 181 ÿ 182, 181
angle sections, buckling curves178ÿ 180, 178 , 179
codes and standards 298, 300 ÿ 303round sections 83, 184 ÿ 185tubular bracing members 184, 184
tubular leg members 184concrete guyed masts
advantages 90disadvantages 90 ÿ 91
concrete towersantenna mounting 72deection advantages 72drag factors 72rst 28 , 71ÿ 72height-to-base ratios 76public access 72steel topmasts, height-to-base ratios 76structure 72 ÿ 73weight 72
connectionsange joints
solid round legs 190ÿ 191, 191
tubular round legs 191 ÿ 192, 191
guy cablesfreedom of rotation 193 , 194, 194
stay plates 192, 192 , 194corrosion
bi-metallic 266concrete 90humidity 94, 115pollution 94
corrosion protectionexternal 86 ÿ 87galvanizing 88, 265, 266guy cables 65
galvanizing 266, 267greasing 266zinc-rich paste 267
tubes, internal 81crack detection, fatigue damage
225ÿ 226, 226
cranked K-bracing systems 188 ÿ 189,188
critical wind speedsgalloping 216ÿ 219, 217vortex shedding 211 ÿ 212
cross-bracing, bracing systems, withhorizontals at centre intersections186 , 187ÿ 188
cross-bracing systems 186ÿ 187, 186
with horizontals at centreintersections 186 , 187ÿ 188
with redundants 186 , 187cross-lays, wire ropes 198Crystal Palace Tower 78, 79
cylindersdrag 120, 121 , 137ÿ 138, 138vortex shedding 213 ÿ 214
strake damping 214, 215
tuned mass dampers 214 ÿ 215
DAB see digital audio broadcastingDanish standard towers 79, 80
guy cables, articulation 104, 193
dead loads 2ÿ 3deection angles, codes and standards
295delta-type low-frequency antennas 40design, corrosion protection, galvanizing
88, 265, 266design faults, guyed masts, failures due
to 61, 62 , 63digital audio broadcasting (DAB)
antenna requirements 33multimedia potential 51multiplex carriers 50reception 50transmitter spacing 51
dipolesbatwing 45ÿ 46, 45
with reector screens 46, 47
screening 36 ÿ 37wind effects 36ÿ 37
dish antennas, wind resistance 100 ÿ 101,118
downthrust resistance, foundations 229,
233, 233 , 234downtime, due to wind speeds 102 ÿ 104,
103
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dragancillaries 128ÿ 132, 129 ÿ 131 , 287
discrete 133guy cables 133ÿ 134, 134 , 144ÿ 145,
145
linear 133Australian code 292circular members 120codes and standards 286 ÿ 287,
288 ÿ 291 , 292crosswinds 127ÿ 128cylinders 120, 121 , 137ÿ 138, 138
dish antennas 118 ÿ 119guyed masts, uctuations 162 ÿ 163icing
coefcients 141ÿ 142, 142guy cables 140light 140ÿ 141, 141
mean loading 117round members 83square structures 117, 118
and angle of incidence 125 ÿ 126,125 , 126
circular section members 124 , 126
at-sided members 123 , 125
wind on corner 290wind on face 288
structural ‘panels’ 118, 119
and surface roughness 138 ÿ 139, 139
triangular structures 117 ÿ 118, 118
ancillaries 129, 129 , 130
angle of incidence 126 ÿ 127, 127 ,128
circular section members 124 , 127 ,129 , 130
at-sided members 123 , 131wind on corner 291
wind on face 289
and turbulence 124 ÿ 125, 139wind tunnel tests 118, 131 ÿ 132,
134ÿ 137, 135 , 136
with ancillaries 135 , 137
discrepancies 137 ÿ 140, 138 , 139
dustfall effects 94, 116dynamic analysis
see also simplied dynamic analysisguyed masts 150ÿ 154, 152
background components 155
bending moment components156ÿ 157, 156
gust factor analysis 168ÿ 170, 168
mean components 154 ÿ 155non-linearity responses 153 ÿ 154resonant components 155 ÿ 156and simplied analysis 168, 168
time domain 148simulation 3
dynamic responsescalculations 147 ÿ 148lattice towers 148, 149 , 150
earthing systemslightning strikes 44, 116low-frequency antennas 40
earthquakes see seismic responseseconomics, balancing 19 ÿ 20, 69ÿ 70Eddystone lighthouses 8, 10
Smeaton’s 8, 10
Winstanley’s 8, 9
effective radiated power (erp)denitions 19maximising 33
Eiffel, Gustave 10ÿ 12Eiffel tower (France) 9 ÿ 12, 11 , 17, 27
broadcasts from 12Electronics Industries Association (EIA)
(USA) 244elevation, sites 21, 21 , 23Emley Moor TV transmitter (1st),
failure, icing 60ÿ 61, 113Emley Moor TV transmitter (2nd) 73,
74
Listed Building Status 28, 75endurance curves, welded details
221ÿ 222, 221
environmental impactEiffel tower 27planning permissions 70tall communications towers 28 ÿ 29
equal lays, wire ropes 198erection 4
guyed masts 260ÿ 263, 262
lattice towers 259 ÿ 260, 260
tolerances, codes and standards 305,306
weather 259
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erp see effective radiated powerEurocode 3 244, 276
reliability classes 280
fabrication 4bolts, yield strength 257faults, failures due to 63poor
ange plates 255, 256
tubular legs 255 ÿ 257, 256
slotted holes 257failures 3ÿ 4
by terrorism 68ÿ 69by vandalism 68ÿ 69, 69
economic considerations 69 ÿ 70fabrication faults 63guyed masts 56ÿ 57, 58
aircraft damage 65 ÿ 66, 66 , 67 , 68design faults 61, 62 , 63maintenance 63, 64 , 65single guy cables 68stay plates 62 , 63
icing 59, 113triggering mechanisms 60
maintenance, procedures 63, 64 , 65,70
fatigue damageassessing 220endurance curves, welded details
221ÿ 222, 221
guy cables 226ÿ 227guyed masts
construction standards 223 ÿ 224crack detection 225 ÿ 226, 226
ange joints 224 ÿ 225, 225
lattice towers 223low cycle 220total 222 ÿ 223vortex excitation 220 ÿ 221wind causes 104, 220
Finland, icing conditions 140 ÿ 141ange joints
poor fabrication 255, 256
solid round legs 190ÿ 191, 191
tubular round legs 191 ÿ 192, 191
foundationsdownthrust resistance 229, 233, 233 ,
234
guy cablesconventional 233 ÿ 235, 235
inverted T 235, 237
tension rod 237 ÿ 238, 238tie rod 236, 237
two stays 235, 236
guyed lattice masts 85 ÿ 86, 85
lattice steel towers 232
overturning resistance 229, 230 , 231tubular guyed masts 88, 89
uplift resistance 228 ÿ 229, 230 , 231,231
freezing snow, icing due to 104, 106fundamental parameters
service area 19signal frequency 19
Gabin mast (Poland), failure, guyreplacement 64 , 65
gain, TV antennas 44 ÿ 45galloping
calculations 216causes 216ÿ 217, 218ÿ 219damping devices 219denition 216iced cables 216ÿ 217, 217spoilers 217wake 218
galvanizingcorrosion protection 88, 265, 266
guy cables 266, 267geotechnical site considerations 275Germany, codes and standards 244glass-bre cylinders, antenna screening
46, 47
glaze icing, formation 104, 106groundwave components, medium-
frequency systems 41gust response factors
lattice steel towers 148, 149
terrain categories 148, 149
gust speeds, and wind speeds 282
guy cablessee also galloping; guy insulators;
vortex shedding
aircraft damage to 66, 67anchorages
conventional 233 ÿ 235, 235
331
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guy cablesanchorages ( continued )
inverted T 235, 237
tension rod 237 ÿ 238, 238tie rod 236, 237
two stays 235, 236
connectionsfreedom of rotation 193 , 194, 194
stay plates 192, 192 , 194corrosion 65corrosion protection
galvanizing 266, 267greasing 266zinc-rich paste 267
fatigue damage 226ÿ 227icing 107, 107
accretion 144 ÿ 145, 145
assymetric loadings due to 109assymetric shedding 113drag coefcient 145formation 108 ÿ 109, 109
wind drag 140ideal parameters 195nomenclature 196, 196
ropesclamped terminations 198core 196lays 196, 197 , 198, 201, 202 , 203locked-coil 199ÿ 200, 199 , 202,
203 , 205
modulus of elasticity 203, 203
non-metallic 201parallel laid wires in a strand 200polypropylene impregnated
200ÿ 201, 201 , 267prestretching 203 ÿ 204, 205 , 206,
304rotational characteristics 202 ÿ 203,
202
spiral strands 198 ÿ 199, 199 , 202 ,203, 205
strength 202use of standard 196
slope, optimum 25still air tensioning 206
temperature effects 114terminations 206 ÿ 207, 304ÿ 305
guy sockets 207, 207 , 208
loops 208, 209
preformed grips 208ÿ 209wind resistance 133 ÿ 134, 134
guy insulatorscosts 27installing 263
guy sockets, terminations 207, 207 , 208
guyed lattice masts 82
failures, maintenance 63, 65foundations, xed 85 ÿ 86, 85
guy cablesdirections 83inclination 83spacing 81ÿ 82, 83twin 84ÿ 85, 84
leg sections 82ÿ 83omnidirectional antennas 82top sections 82torsional restraint
arms 85, 85
twin guys 84ÿ 85, 84
vertical thrust 82weight 89ÿ 90
guyed masts 17see also concrete guyed masts; guy
cables; guyed lattice masts;tubular guyed masts
aircraft damage 65 ÿ 66, 66 , 67 , 68bases, pinned 167cantilevers
erection 263guy tensions 174, 175
patch load analysis 170 ÿ 171codes and standards, deection limits
243ÿ 244design faults, failures due to 61, 62 ,
63dynamic analysis 150ÿ 154, 152
see also guyed masts, simpliedanalysis
background components 155bending moment components
156ÿ 157, 156
gust factor analysis 168ÿ 170, 168
mean components 154 ÿ 155
non-linearity responses 153 ÿ 154resonant components 155 ÿ 156and simplied analysis 168, 168
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erection 258 ÿ 261, 260
failures 56ÿ 57, 58
bracing rods 63, 65during guy replacement 64 , 65ice loading 59ÿ 61stay plates 62 , 63
fatigue damageconstruction standards 223 ÿ 224crack detection 225 ÿ 226, 226
ange joints 224 ÿ 225, 225
guy supports, analysis 173, 173
guy tensionsgust factors 174patch load methods 174 ÿ 175
height, determinants 25 ÿ 26multi-purpose, compromises 26 ÿ 27seismic responses 91, 273ÿ 274simplied analysis 159ÿ 161
bending moment responses 165,165
and dynamically sensitive masts 167patch load methods 160 ÿ 164, 162 ,
167ÿ 168, 168 , 169ÿ 172, 171 ,172
static procedures 164 ÿ 165, 166 ,167
single cable failure 68square 24, 25
stay lanes, elevation 24 ÿ 25time domain analysis 148, 157 ÿ 159,
159
advantages 157aerodynamic damping 158turbulence simulation 158 ÿ 159,
159
triangular 24, 25turbulance, modes 150, 151
vandalism 68 ÿ 69, 69
vortex shedding, damping 215warning lights 66weight 17wind load uctuations 162 ÿ 163
hail effects 94health and safety see safety
height-to-base ratiosconcrete towers 76
with steel topmasts 76
lattice steel towers 75 ÿ 76horizontal radiation patterns,
omni-directional 35 ÿ 37, 37 , 38 ,44
Houston mast (USA), maintenancefailure 63
humidity effects, corrosion 94, 115hybrid connections 184, 184
IASS see International Association of Shell and Spatial Structures
icing 2, 94, 110
codes and standards 242, 292drag
coefcients 141ÿ 142, 142
radiused corners 143 ÿ 144, 143failures due to 59
guyed masts 59ÿ 61triggering mechanisms 60
freezing snow 104, 106galloping 216ÿ 217, 217
glaze 104, 106
growth rates 107 ÿ 108guy cables 107, 107
accretion 144 ÿ 145, 145
assymetric loadings due to 109assymetric shedding 113formation 108 ÿ 109, 109
wind drag 140lattice towers 59, 59
light, drag 140ÿ 141, 141
loadings, codes 242loads due to 106 ÿ 107
estimating 110 ÿ 111precipitation 59 ÿ 60rime 104, 105 , 106
formation 108hard 104, 105 ÿ 106soft 104ÿ 105
risk assessments 111and vortex shedding 60 ÿ 61zoning map, UK 111 ÿ 112, 112
inspection programmes 70insulators
codes and standards 305 ÿ 306
guy, costs 27lightning strikes 116
interference, between antennas 54 ÿ 55
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International Association of Shell andSpatial Structures (IASS) 244
access safety recommendations248ÿ 250, 249
masts and towers 308 ÿ 310reliability classes 281
International Aviation Organization(IAO), aircraft warnings 66, 265
international frequency rangesradio 31, 32 , 37television 31, 32
K-bracing systems 188, 188
cranked 188 ÿ 189, 188
ladder types, access safety 249Lang’s lay, wire ropes 198, 201lattice steel towers
see also guyed lattice mastsantenna attachments 77 ÿ 78building mounted, seismic responses
272cantilevers 86codes and standards 279costs 27cylindrical sections 86Danish standard 79, 80
diagonals, bolted connections 79, 81,81
dynamic responses 148, 149, 149
gusts 148, 149
erection 258 ÿ 260, 260
fatigue damage 223foundations 232
height-to-base ratios 75 ÿ 76heights 75icing 59, 59
internal corrosion 81as relay stations 76ÿ 77, 77
sections 78ÿ 79round bars 86 ÿ 87tubular connections 79, 80
seismic responses 272ÿ 273torsional rigidity 76, 77turbulence modes 150, 151
vortex shedding 212 ÿ 213lattice towers, glass reinforced plastic
259
layswire ropes 196, 197 , 198
cross- 198equal 198Lang’s 198, 201ordinary 198
lighthouses, Eddystone 8, 9 , 10
lightning strikes 94, 115 , 116earthing 44, 116insulators 116medium-frequency systems 43
Lisnagarvey mast 43, 43
Listed Building Status, Emley Moor TVtransmitter 28, 74 , 75
local and torsional buckling 178 ,180ÿ 181
locked-coil ropes 199ÿ 200, 199
prestretching 204, 205 , 206loop terminations, guy cables 208, 209
low temperature embrittlement, steel 115low-frequency antennas 37 ÿ 40, 38 , 39
capacitance discs 41delta-type 40design objectives 38earthing systems 40T-type 40, 40umbrella designs 38ÿ 40, 39
maintenance 5, 70constraints 264 ÿ 265failures during, clamp failures 63manuals 267 ÿ 268minimizing, at design stages 265ÿ 267programmes 70
Marconi, Guglielmo 12 ÿ 13medium-frequency systems
column length, base impedance 43current distributions 42 ÿ 43, 42
groundwave components 41lightning strikes 43 ÿ 44skywave components 41static 43
microwave dish antennas, plan rotation36
mobile phones see cellular phones
modulus of elasticityropes 203, 203
variability 204
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monopoles, seismic responses 273Moscow Tower (Russia) 72Mount Sutro Tower (USA) 47, 48
multi-purpose antennas, compromises26ÿ 27, 33ÿ 34
multiple lattice bracing systems 188 ,189
multiplex carriers, digital audiobroadcasting 50
ordinary lays, wire ropes 198overturning resistance, foundations 229,
230 , 231
panel antennas 48, 49
parallel laid wires in a strand 200partial safety factors, codes and
standards 295 ÿ 298planning permissions, environmental
impact 70plastics
lattice structures 259shell radomes 259ÿ 260sunlight degradation 94, 115‘tree’ communication towers 30, 30 ,
258pollution effects, corrosion 94polypropylene impregnated ropes
200ÿ 201, 201 , 267portal frame bracing systems 188 , 189Post Ofce Tower 74
bomb attack 68structure 73
precipitation icing 59 ÿ 60preformed grip terminations, guy cables
208ÿ 209
radiation patternshorizontal, omni-directional 35 ÿ 37,
37 , 38 , 44vertical 34ÿ 35, 35 , 36
radiodigital broadcasting, antenna
requirements 33France 12
international frequency ranges 31, 32 ,37
relay stations 76 ÿ 77, 77
timber towers 71UK 13ÿ 15
redundants see stabilizing membersrelay stations
directional importance 77, 78
lattice steel towers 76 ÿ 77, 77 , 78
Reynold’s numberdenition 120icing, drag coefcients 141ÿ 142, 142
rime ice 105 , 106
formation 108, 108
hard 104, 105 ÿ 106soft 104ÿ 105
risk assessmentsicing 111terrorism 69
ropes, non-metallic 201ropes (steel)
clamped terminations 198core 196lays
cross-ropes 198equal 198Lang’s 198, 201ordinary 198, 202 , 203, 205
wire 196, 197 , 198locked-coil 199ÿ 200, 199 , 202 , 203
prestretching 204, 205 , 206modulus of elasticity 203, 203
variability 204parallel laid wires in a strand 200polypropylene impregnated 200 ÿ 201,
201
prestretchingconstructional 203, 304curves 204, 205cyclical 204
rotational characteristics 202 ÿ 203,202
spiral strands 198 ÿ 199, 199 , 202 , 203prestretching 204, 205 , 206
strength 202use of standard 196
round sectionssee also tubes
compression strength 83, 184 ÿ 185solid, ange joints 191, 191
wind resistance 83, 86, 120
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safetyaccess 33
climb duration 247climber competency 250guidelines 246ÿ 247ladder types 249sophistication of 248
IASS recommendations 248 ÿ 250, 249
legal requirements 5training schemes 246
security, sites, vandalism 68 ÿ 69, 69
seismic responses 3, 94, 113ÿ 114,269ÿ 270
antennas 275categories 270ÿ 271geotechnical site considerations 275guyed masts 91, 273ÿ 274lattice towers 272 ÿ 273monopoles 273peak ground accelerations 271sensitivity predictions 271 ÿ 272
service area, plan 19serviceability components 4serviceability factors, codes and
standards 293 ÿ 295, 294
serviceability limits, and windpredictions 102 ÿ 104, 103
shadow effects, VHF/UHF systems 49shell radomes, plastic 258signal range, broadcast frequency 21 ÿ 22,
22
simplied dynamic analysisguyed masts 159ÿ 161
bending moment responses 165,165
and dynamically sensitive masts167
and full analysis 168, 168
patch load methods 160 ÿ 164, 162 ,167ÿ 168, 168 , 169ÿ 172, 171 ,172
static procedures 164 ÿ 165, 166 ,167
single lattice bracing systems 186, 186
sites
broadcast frequency 21 ÿ 23, 22elevation 21, 21 , 23geotechnical considerations 275
multi-purpose structures 22parameters 23selection parameters 20service area 20ÿ 21
Sjællands Odde tower (Denmark) 130,132
skywave components, medium-frequencysystems 41
snow see icingsolar heating 114
tilt effect 35spiral strand ropes 198 ÿ 199, 199 , 202 ,
203, 205
prestretching 204, 205 , 206square structures
wind effects 100, 100wind resistance 117, 118
stabilizing membersK bracing 185triangular structures 185 ÿ 186value of 185
standards see codes and standardsstatic, medium-frequency systems 43stayplates, failure of 62 , 63steel
see also fabrication; ropes (steel)angle 254, 300
buckling curves 178 ÿ 180, 178 , 179
strength 301 ÿ 302, 302
Charpy V-notch testsnormalization252 252
specications 253 ÿ 254chemical composition 253, 254circular 300
corrosion protection 86 ÿ 87galvanising 88, 265, 266
low temperature embrittlement 115mild
high-yeild stress 253strengths 251
plates, cutting 257rapid loading, brittle fractures 252round 254 ÿ 255
brittle failures 255compression resistance 83
residual stresses 255wind resistance 83, 86, 120
temperatures, service 251, 253, 254
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tubescosts 79diagonal connections to 79, 80 , 81
welding, fracture toughness 253still air tensioning, guy cables 206strength components 4strengths see compression strengths;
local and torsional bucklingStuttgart Tower (Germany) 28 , 71sunlight degradation, plastics 94, 115
T-type low-frequency antennas 40, 40
televisionantennas
see also guyed mastsmaximum service area 24
digital broadcasting, antennarequirements 33
earlyFrance 13UK 15ÿ 17, 16
international frequency ranges 31, 32
temperature effects 94guy cables 114low extremes 114 ÿ 115
steel embrittlement 115, 251solar heating 114tilt effect 35
tensile strength, codes and standards303ÿ 304
tension, strength in 190tension bracing systems 186 , 187terrain categories, gust response factors
148, 149
terrorism, risk assessments 69Teutoberger mast (Germany), design
faults 62 , 63tilt, antennas, due to solar heating 35timber towers 71, 257 ÿ 258
radio transparency 71, 257time domain analysis
guyed masts 148, 157ÿ 159, 159
advantages 157aerodynamic damping 158turbulence simulation 158 ÿ 159,
159topography
aerial coverage 21, 21
and wind speeds 283 ÿ 284, 284 , 285 ,286
Torre de Collserola (Spain) 29, 29
construction 91torsional and local buckling 178 ,
180ÿ 181torsional restraint
arms 85, 85
twin guys 84ÿ 85, 84
torsional rigidity, lattice steel towers 76,77
Tower of Babel 6, 7
Tower of Pharos 6, 7 , 8towers
see also communication towers;concrete towers; lattice steeltowers; timber towers
church 8in history 6, 7 , 8lighthouses 8, 9 , 10
‘tree’ communication towers 30, 30 ,258
triangular structuresstabilizing members 185ÿ 186wind effects 100, 100
wind resistance 117 ÿ 118, 118tubes
costs 79diagonal connections to 79, 80 , 81internal corrosion 81
tubular bracing members 184, 184
tubular guyed masts 88
advantages 87corrosion protection 88disadvantages 87foundations 88, 89guy planes 88internal access lifts 88structure 87 ÿ 88weight 89ÿ 90
tubular leg memberscompression strengths 184fabrication, poor 255 ÿ 257, 256
ange joints 191 ÿ 192, 191
turbulence
modesguyed masts 150, 151
lattice towers 150, 151
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turbulencemodes (continued )simulation, time domain analysis
158ÿ 159, 159and wind resistance 124 ÿ 125, 139
UHF systems see VHF/UHF systemsultimate loads, wind effects, probability
of exceedance 97 ÿ 98, 98
United Kingdombroadcasting development
radio 13ÿ 15television 15 ÿ 17, 16
codes and standards 245, 276reliability standards 281
ice zoning map 111 ÿ 112, 112uplift resistance, foundations 228 ÿ 229,
230 , 231, 231
USAcodes and standards 244, 276
reliability classes 281
vandalism, guyed masts 68ÿ 69, 69
vertical radiation patterns 34 ÿ 35, 35 ,36
VHF/UHF systemsantenna mountings
candelabra type 47, 48
dipoles 45ÿ 46, 45 , 46
glass-bre cylinders 46, 47
maintenance 46panels 48, 49
shadow effects 49verticality, importance of 48 ÿ 49
vortex excitation, fatigue 220 ÿ 221vortex shedding
causes 211ÿ 212, 212
critical wind speeds 211 ÿ 212cylindrical masts 213ÿ 214damping devices
strakes 214, 215
tuned mass dampers 214 ÿ 215guyed masts, damping 215and ice loading 60ÿ 61
wake galloping 218welded details, endurance curves
221ÿ 222, 221
welding, steel, fracture toughness 253wind climates 93 ÿ 94
atmospheric circulation 95 ÿ 97, 95
boundary layer 99extreme speeds 96, 97 ÿ 98, 98
wind directions, critical 100, 100
wind loadings 2see also dragcurves
BBC 239ÿ 240, 240
early 241ÿ 242, 241
dipoles 36dish antennas 100 ÿ 101fatigue damage 104height relationships 99 ÿ 100square structures 100, 100
topographical factors 101 ÿ 102triangular structures 100, 100
turbulence 99ultimate, probability of exceedance
97ÿ 98, 98
vertical wind prole 101vortex shedding, ice 60 ÿ 61
wind predictions 102and serviceability limits 102 ÿ 104, 103
wind resistance see dragwind speeds
and altitude 282 ÿ 284, 283
downtime due to 102 ÿ 104, 103
and gust speeds 282
and topography 283 ÿ 284, 284 , 285 ,286
wind tunnelsdrag tests 118, 131 ÿ 132, 134ÿ 137, 136
with ancillaries 135 , 137
discrepancies 137 ÿ 140, 138 , 139
early use of 11ÿ 12wire ropes see guy cables; lays
Yllas mast (Finland), failure, icing 60,61, 113
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