Communication Structures

Contents
Foreword ix
Preface xi
Acknowledgements xiii
Chapter 1 Introduction 1
Chapter 2 History 6
Chapter 3 Design considerations 19
3.1 General, 19
3.2 Choice of site, 20
3.3 Choice of structure, 24
3.4 Economic considerations, 27
3.5 Environmental considerations, 27
3.6 Electronic considerations, 30
3.6.1 General, 30
3.6.2 Antenna characteristics, 33
3.6.3 Low-frequency antennas, 37
3.6.4 Medium-frequency antenna systems, 41
3.6.5 VHF and UHF antennas, 44
3.6.6 Digital audio broadcasting, 49
3.6.7 Mobile phone antennas, 51
3.7 Effect on existing services of subsequent additional
antenna, 54
Chapter 4 Failures of masts and towers 56
4.1 General, 56
4.2 Icing failures, 59
4.3 Design/detail failures, 63
4.4 Maintenance failures, 63
4.5 Aircraft damage, 65
4.6 Vandal damage, 68
4.7 Lessons to be learned, 69
Chapter 5 Forms of structure 71
5.1 General, 71
5.2 Timber towers, 71
5.3 Concrete towers, 71
5.4 Lattice steel towers, 75
5.5 Lattice guyed masts, 81
5.6 Tubular guyed masts, 87
5.7 Concrete guyed masts, 90
5.8 Other forms of communication structures, 91
Chapter 6 Meteorological parameters 93
6.1 General, 93
6.2 Wind, 93
6.2.1 Wind climate, 95
6.2.2 Boundary layer, 99
6.2.3 Serviceability wind speeds, 102
6.3 Atmospheric icing, 104
6.3.1 General, 104
6.3.2 Physics and theoretical modelling of ice accretion, 107
6.3.3 Empirical models to estimate ice loads on
structures, 109
6.4 Earthquakes, 113
6.5 Temperature, 114
6.6 Other meteorological aspects, 115
Chapter 7 Wind resistance 117
7.1 General, 117
7.2 Symmetrical structures without ancillaries, 122
7.3 Symmetrical structures with limited ancillaries, 128
7.4 General method for structures containing
ancillaries, 129
7.5 Linear ancillaries, 133
7.6 Discrete ancillaries, 133
7.7 Cables, 133
7.8 Measurements on scale model of communications
tower, 134
7.9 Discrepancy between wind tunnel tests and full-scale
measurements,137
7.10 Icing, 140
Chapter 8 Response 147
8.1 General, 147
8.2 Lattice towers, 148
8.3 Guyed masts, 150
8.3.1 General, 150
8.3.2 Frequency domain analysis, 152
8.3.3 Time domain analysis, 157
8.3.4 Simplified methods, 159
8.3.5 Summary, 176
Chapter 9 Strength 177
9.1 Introduction, 177
9.2 Design against buckling – individual members, 178
9.2.1 General, 178
9.2.2 Influence of local and torsional buckling, 180
9.2.3 Angle leg members, 181
9.2.4 Angle bracing members, 182
9.2.5 Tubular leg members, 184
9.2.6 Tubular bracing members, 184
9.2.7 Solid round members, 184
9.3 Secondary members (‘redundants’), 185
9.4 Bracing types, 186
9.5 Compound members, 189
9.6 Tension, 190
9.7 Connections, 190
9.7.1 General, 190
9.7.2 Flange joints in tubular or solid round leg
members, 190
9.7.3 Guy connections, 192
Chapter 10 Cables 195
10.1 General, 195
10.2 Types of cables, 195
10.3 Strength of guy ropes, 202
10.4 Rotational characteristics of steel ropes, 202
10.5 Modulus of elasticity, 203
10.6 Prestretching, 2013
10.7 Still air tension, 206
10.8 Terminations, 206
10.8.1 General, 206
10.8.2 Types of terminations, 207
Chapter 11 Aerodynamic stability 210
11.1 General, 210
11.2 Vortex shedding, 211
11.2.1 General, 211
11.2.2 Background and critical wind speed, 211
11.2.3 Practical implications, 213
11.2.4 Damping devices, 214
11.3 Galloping, 216
11.3.1 General, 216
11.3.2 Critical wind speed, 216
11.3.3 Damping devices, 219
Chapter 12 Fatigue 220
12.1 General, 220
12.2 Lattice towers, 223
12.3 Lattice masts, 223
12.4 Guys, 226
Chapter 13 Foundations 228
13.1 General, 228
13.2 Foundation types, 228
13.2.1 Type 1: to resist uplift, 228
13.2.2 Type 11: to resist overturning, 231
13.2.3 Type 111: to resist down thrust, 233
13.2.4 Type IV: guy anchorages, 233
Chapter 14 Codes and standards 239
14.1 History, 239
14.1.1 General, 239
14.1.2 Wind loading, 239
14.1.3 Ice loading, 242
14.1.4 Strength, 243
14.1.5 Other aspects, 243
14.2 Current codes, 244
14.2.1 General, 244
14.2.2 Comparison of current Codes, 245
Chapter 15 Access and safety 246
15.1 General, 246
15.2 IASS Recommendations for safe access, 249
Chapter 16 Fabrication and erection 251
16.1 Materials and fabrication, 251
16.1.1 Steel for towers and mast columns, 251
16.1.2 Aluminium, 257
16.1.3 Timber, 257
16.1.4 Plastics, 258
16.2 Erection, 258
16.2.1 General, 258
16.2.2 Erection of lattice towers, 259
16.2.3 Erection of guyed masts, 259
Chapter 17 Maintenance 264
17.1 General, 264
17.2 Constraints, 264
17.3 Minimizing maintenance at the design stage, 265
17.4 Manuals, 267
Chapter 18 Seismic response 269
18.1 General, 269
18.2 Seismicity and earthquake-resistance performance levels, 270
18.3 Prediction of seismic response of structures, 271
18.3.1 General , 271
18.3.2 Self-supporting lattice towers, 272
18.3.3 Monopoles, 273
18.3.4 Guyed masts, 273
18.3.5 Antennas and ancillary components, 275
18.4 Geotechnical considerations, 275
Annex A Codes of Practice and Design Standards 276
A.1 General, 276
A.2 Comparisons of National Codes,277
A.3 Scope, 277
A.4 Limit states/reliability classes, 277
A.5 Wind structure, 279
A.5.1 General, 279
A.5.2 Wind resistance, 286
A.6 Ice loading, 292
A.7 Displacements/serviceability, 293
A.8 Partial safety factors, 295
A.9 Strength, 298
A.9.1 Compressive strength, 298
A.9.2 Tensile strength, 303
A9.2.1 Steel structure, 303
A9.2.2 Guys, 303
A.10 Guy assemblies, 304
A.10.1 General, 304
A.10.2 Prestretching, 304
A.10.3 Terminations, 304
A.10.4 Initial tensions, 305
A.11 Erection, 305
A.12 Insulators, 305
A.13 Access, 307
Annex B IASS Working Group Number 4: Masts and
Towers 308
B.1 Brief history, 308
B.2 Role in the future, 308
B.3 The members of the Group, 309
References 311
Index 327