Lattice Steel Towers and Steel Poles
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Transcript of 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
March 2011
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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.
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011
Lattice Steel Towers
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011
-
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20/07/2011
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Lattice Steel Towers Destruction test.
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011
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.
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011
-
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20/07/2011
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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.
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011
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.
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011
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.
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
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.
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011
-
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6/7
20/07/2011
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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.
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011
Steel Monopoles
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011
-
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20/07/2011
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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.
Australian Panel B2 Overhead Line
Design Seminar AS/NZS 7000:2010
Overhead Line Design Sydney 28 & 29
March 2011