AS 3995-1994

Design of steel lattice towers and masts

Standards Australia

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1 - AS 3995:1994 DESIGN OF STEEL LATTICE TOWERS AND MASTS
4 - PREFACE
5 - CONTENTS
6 - SECTION 1 - SCOPE AND GENERAL
6 - 1.1 SCOPE
6 - 1.2 REFERENCED DOCUMENTS
7 - 1.3 DEFINITIONS
7 - 1.3.1 Bracing members
7 - 1.3.2 Leg members
7 - 1.3.3 Linear ancillaries
7 - 1.3.4 Secondary bracing members
7 - 1.4 NOTATION
12 - 1.5 TYPE OF STRUCTURE
12 - 1.5.1 Type I
12 - 1.5.2 Type II
12 - 1.5.3 Type III
12 - 1.6 LOADING
12 - 1.6.1 Dead loads (G)
12 - 1.6.2 Wind loads (Wu, Ws)
12 - 1.6.3 Ice loads (I)
12 - 1.6.4 Earthquake loads
12 - 1.6.5 Load combinations
13 - 1.6.6 Incidental loads on members
13 - 1.7 STABILITY LIMIT STATE
13 - 1.8 STRENGTH LIMIT STATE
13 - 1.9 SERVICEABILITY LIMIT STATE
15 - SECTION 2 - WIND LOAD SPECIFICATIONS
15 - 2.1 DESIGN PROCEDURES
15 - 2.2 STATIC ANALYSIS
15 - 2.2.1 General
17 - 2.2.3 Terrain and height multiplier (M(z, cat))
17 - 2.2.3.1 Terrain category
17 - 2.2.3.2 Terrain multiplier
17 - 2.2.4 Topographic multiplier
18 - 2.2.5 Wind direction multiplier
20 - 2.2.6 Calculation of drag forces
21 - 2.2.7 Dynamic wind pressure
21 - 2.2.8 Drag force coefficient
21 - 2.2.8.1 General
21 - 2.2.8.2 Tower sections without ancillaries
24 - 2.2.8.3 Tower sections with ancillaries
24 - 2.2.8.4 Correction factor for interference
26 - 2.3 DYNAMIC ANALYSIS
26 - 2.3.1 General
26 - 2.3.2 Mean wind speed
26 - 2.3.3 Terrain and height multiplier (M(z, cat))
26 - 2.3.3.1 Terrain category
26 - 2.3.3.2 Terrain multiplier
26 - 2.3.4 Topographic multiplier
27 - 2.3.5 Along-wind response
28 - 2.3.5.1 Limitations
28 - 2.3.5.2 Design load effects
29 - 2.3.6 Cross-wind response
29 - 2.3.7 Serviceability design
29 - 2.3.8 Gust response factor for freestanding lattice towers
31 - SECTION 3 - STRUCTURAL ANALYSIS AND DESIGN
31 - 3.1 STRUCTURAL ANALYSIS
31 - 3.1.1 General
31 - 3.1.2 Guyed masts
31 - 3.2 GENERAL DESIGN REQUIREMENTS
31 - 3.2.1 General
31 - 3.2.2 Minimum sizes
31 - 3.2.3 Limiting slenderness ratios
32 - 3.3 COMPRESSION MEMBERS
32 - 3.3.1 Member compression capacity
32 - 3.3.2 Member slenderness reduction factor
33 - 3.3.3 Effective compression area
34 - 3.3.4 Effective slenderness ratios
34 - 3.3.4.1 General
34 - 3.3.4.2 Leg members
34 - 3.3.4.3 Bracing members
34 - 3.3.4.4 Secondary bracing members
35 - 3.3.4.5 Member end restraints
35 - 3.3.5 Compound leg members
35 - 3.3.6 Mast leg members
35 - 3.3.7 Restraint forces in secondary bracing members
36 - 3.4 TENSION MEMBERS
36 - 3.4.1 General
36 - 3.4.2 Guy tension members
36 - 3.4.2.1 General
36 - 3.4.2.2 Guy tension members
37 - 3.4.2.3 Distribution of forces
37 - 3.5 CONNECTIONS
37 - 3.5.1 General
37 - 3.5.2 Welded connections
37 - 3.5.3 Bolted connections
37 - 3.5.4 Bolted connections using tower bolts
37 - 3.5.4.1 General
39 - 3.5.4.2 Bolts in shear
39 - 3.5.4.3 Bolts in tension
39 - 3.5.4.4 Bolts subject to combined shear and tension
39 - 3.5.4.5 Ply in bearing
40 - 3.5.4.6 Detail requirements
41 - SECTION 4 - FOOTING DESIGN
41 - 4.1 GENERAL
41 - 4.2 PERFORMANCE OF FOOTINGS
41 - 4.3 SOIL PROPERTIES
41 - SECTION 5 - CRITERIA FOR ASSESSMENT OF EXISTING STRUCTURES
41 - 5.1 STRUCTURAL ASSESSMENT
41 - 5.2 GENERAL DESIGN REQUIREMENTS
42 - APPENDIX A - MAINTENANCE AND INSPECTION
42 - A1 GENERAL
42 - A2 SCOPE OF MAINTENANCE INSPECTION
42 - A3 MAINTENANCE INSPECTION FREQUENCY
43 - A4 SCHEDULED MAINTENANCE AND REPAIRS
43 - A5 ELECTRICAL HAZARDS
44 - APPENDIX B - ACCESS TO STEEL LATTICE TOWERS AND MASTS
44 - B1 GENERAL
44 - B2 DESIGN
44 - B3 DESIGN LOADING
44 - B4 CLASSIFICATION OF STRUCTURE
44 - B4.1 Class A
44 - B4.2 Class B
44 - B4.3 Class C
44 - B5 ACCESS RECOMMENDATIONS
44 - B5.1 Class A structures
44 - B5.2 Class B structures
45 - B5.3 Class C structures
46 - APPENDIX C - GUIDANCE FOR EARTHQUAKE DESIGN
47 - APPENDIX D - ESTIMATION OF THE FIRST MODE NATURAL FREQUENCY
49 - APPENDIX E - GUIDANCE FOR DETERMINATION OF WIND LOADS
49 - E1 GUST WIND SPEED
49 - E2 TERRAIN AND HEIGHT MULTIPLIER
49 - E2.1 Terrain multiplier
50 - E3 TOPOGRAPHIC MULTIPLIER
51 - E4 WIND DIRECTION MULTIPLIER
51 - E5 TOWER SECTIONS WITH ANCILLARIES
51 - E6 CROSS-WIND RESPONSE
51 - E7 GUST RESPONSE FACTOR FOR FREESTANDING LATTICE TOWERS
53 - APPENDIX F - DRAG FORCE COEFFICIENTS (Cda) FOR ANCILLARIES AND ASPECT RATIO CORRECTION FACTORS (Kar)
53 - F1 INTRODUCTION
53 - F2 ROUNDED CYLINDRICAL SHAPES
55 - F3 SHARP-EDGED PRISMS
55 - F4 RECTANGULAR PRISMATIC SECTIONS
56 - F5 ASPECT RATIO CORRECTIONS
56 - F6 DISH ANTENNAS
57 - APPENDIX G - GUIDANCE FOR STRUCTURAL ANALYSIS AND DESIGN
57 - G1 FREESTANDING LATTICE TOWERS
57 - G2 GUYED MASTS
58 - G3 SINGLE BOLTED COMPRESSION MEMBERS
58 - G4 EFFECTIVE SLENDERNESS RATIOS FOR COMPRESSION MEMBERS
58 - G5 GUY TENSION MEMBERS
58 - G5.1 Nominal section capacity
58 - G5.2 Distribution of forces
59 - G6 WELDED CONNECTIONS
60 - APPENDIX H - SLENDERNESS RATIO FOR COMPRESSION MEMBERS
60 - H1 GENERAL
60 - H2 LEG MEMBERS
60 - H3 BRACING MEMBERS
64 - APPENDIX I - GUIDANCE FOR FOOTING DESIGN
64 - I1 GENERAL
64 - I2 PERFORMANCE OF FOOTINGS
65 - I3 SOIL PROPERTIES
66 - APPENDIX J - REFERENCES

Abstract

This Standard sets out procedures for the determination of design wind speeds and wind loads to be used in the structural design of steel lattice towers and masts for communication purposes. It further sets out the basis for the strength assessment of members and connections of lattice towers and masts. This Standard incorporates design and analysis of guyed lattice towers and masts, design of cable tension members, footing design and criteria for assessment of existing structures. Guidance relating to maintenance and inspection, and access to steel lattice towers and masts is given in the Appendices. It is not intended to apply to the structural design of transmission line structures. The design of aluminium and cold-formed steel, other than those complying with AS 1163, is not covered by this Standard, except in relation to access to the lattice towers and masts.

Scope

This Standard sets out the procedures for determination of design wind speeds and wind loads, and other appropriate standards to be used in the structural design of steel lattice towers and masts, with or without ancillaries such as antennas, for communication purposes. It also applies to other lattice towers and masts where the predominant load is wind load on the structure. It further sets out the basis for the strength assessment of members and connections of lattice towers and masts.

This Standard is not intended to apply to the structural design of transmission line structures. The design of cold-formed steel, other than those complying with AS 1163, and aluminium is not covered by this Standard.

For all other aspects of design not specifically mentioned herein, reference shall be made to the appropriate Australian Standards including AS 1170 Parts 1 and 2, AS 1554, AS 1559, AS 1650, AS 3569 and AS 4100.

NOTES:
1 A general framework for maintenance and inspection of existing structures is given in Appendix A.
2 Recommendations for access to steel lattice towers and masts are given in Appendix B. If required by the Health and Safety Authority, provision of safe access to such structures should be considered at the design stage.

General Product Information

Published
Document Type	Standard
Status	Current
Publisher	Standards Australia
Pages
ISBN
Committee	BD-073
Supersedes	AS 3995(Int)-1991 DR 93147