lattice steel towers and steel poles

8/12/2019 Lattice Steel Towers and Steel Poles

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Lattice Steel Towers and Steel Poles

Section 8, Appendix G, Appendix K

Robert Lake

Senior Development Engineer

Transpower NZ Ltd.

Lattice Steel Towers

Mainly self supporting towers;

Reference to other designstandards AS3995, AS4100,NZS3404, ASCE 10-97;

Appendix G guidelines forstructure analysis;

Column(s) of guyed structures isspecial type of lattice tower seesection 8.2.7 for requirements.

Australian Panel B2 Overhead Line

Design Seminar AS/NZS 7000:2010

Overhead Line Design Sydney 28 & 29

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Lattice Steel Towers Note corrosion protection and finishing requirements:

Galvanised to AS/NZS4680 or equivalent;

Thermal spraying is option for oversize sections;

Initial painting over galvanising for improveddurability. (Subsequent painting for life extension);

Weather-resistant steels special requirements.Used in Tasmania.

Full scale load testing to IEC60652 multiple loadcases for a given structural geometry.




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Lattice Steel Towers




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Lattice Steel Towers Destruction test.




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Lattice Steel Towers Calculation of member forces and

moments:

Many load cases, combinations;

Configurations of leg extensionsincluding for crossfall short/long;

Elastic 3D trusses/frames withpinned/fixed end connections;

Pinned simplifies the analysis butmay not allow eccentric loads tobe completely accommodated.




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Lattice Steel Towers Generally first-order linear elastic analysis;

Flexible structures and guyed structuresrequire a second-order analysis which takesinto account P- effects;

Inconsistencies in results when analysingexisting structures that were designed usinghistorical hand methods due to inherentassumptions;

It is generally unnecessary to design fordeflections or vibrations of lattice steeltowers.




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Lattice Steel Towers CIGR TB387;

24 different companiesanalysed towers;

Good agreement;

In full scale test, mainmembers compared well,and diagonal members indirection of load, but notas good for lightly loadedmembers.




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TRANSVERSEFACETRANSVERSEFACETRANSVERSEFACE


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Lattice Steel Towers Guidance also provided for the following: Wide base towers requiring unusual leg

arrangements i.e. cranked K bracing andportal frames;

Secondary (redundant) members in first-order analysis designed for % of supportedmember. Was 2.5% of leg member, nowreduced to 1.77% for members inclined 10(effectively horizontal) and 1.25% for

members inclined > 10; Simple guideline for stub anchorage design.




March 2011

Steel Monopoles

Mainly monopoles but can bemultiple for PI poles;

Off the shelf and specials;

Reference to other design

standards AS/NZS4677,AS/NZS4600, AS4100, andASCE48-05;

Could be guyed as well;

Can be architectural elements.




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Steel Monopoles Note corrosion protection and finishing

requirements:

Galvanised to AS/NZS4680 or equivalent;

Thermal spraying is option for oversizesections and often used;

Initial painting over galvanising for improveddurability. (Subsequent painting for lifeextension).

Full scale load testing to IEC60652 multipleload cases for a given configuration;

May only test unique parts, e.g. crossarms.




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Steel Monopoles




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Steel Monopoles Strength factor generally 0.9;

Low temperature requirements;

Thick base plates welding;

Hydrogen embrittlement issues;

Internal surface performance;

Slip jointing - > 1.5 times diam.;

Anchor bolts;

Electrical earthing.




March 2011

lattice steel towers and steel poles

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