NEW STANDARD A QUANTUM LEAP FOR STEEL
THE STEEL USED TO CONSTRUCT EVERYTHING FROM PREFABRICATED FRAMEWORK AND FACADES, THROUGH TO LIGHTING POLES AND FENCES, IS THE FOCUS OF A NEWLY PUBLISHED STANDARD, BACKED BY THE LATEST AUSTRALIAN RESEARCH AND TECHNOLOGY.
AS/NZS 4600:2018 – Cold-formed steel structures was published in May 2018, following consultation with stakeholders across Australia and New Zealand. The new edition has substantial changes compared with the 2005 edition, endowing it with the potential to be a primary reference in the National Construction Code 2019.
“This new Standard is a quantum leap forward for the steel industry,” said Professor Greg Hancock, Chair of the Standards Australia Technical Committee responsible for the Standard. “This is a world leading Standard that places Australia at the top of the list in terms of the most innovative steel consumers.”
“This new Standard is a quantum leap forward for the steel industry. This is a world leading Standard that places Australia at the top of the list in terms of the most innovative steel consumers.”
Professor Greg Hancock, Chair of the Standards Australia Technical Committee responsible for AS/NZS 4600:2018 – Coldformed steel structures.
The type of steel covered by AS/NZS 4600:2018, often referred to as light gauge steel, is in high demand in the construction sector, delivering safety and durability, strength and flexibility. Light gauge steel is now so light and so strong that it can be used in impressively long spans, negating the necessity for load bearing walls.
Prefabricated modular construction and light gauge steel work well together, particularly in frameworks and facades. Light gauge steel frameworks are useful in constrained pre-fab sites, offering compressed erection times compared to traditional construction methods.
The benefits that AS/NZS 4600:2018 offers to the pre-fab construction industry include lighter weight for transportation and lifting, simpler connections with screws and power actuated fasteners compared with bolting and welding, and innovative roll-formed structural sections appropriate for modular and mid-rise construction.
CHANGES TO AS/NZS 4600
The Direct Strength Method (DSM) of design has undergone substantial research since the 2005 edition of AS/NZS 4600 was published; this research now features heavily in the revised Section 7 – Direct Strength Method (DSM) of Design.
Section 7 now covers sections with holes and inelastic reserve capacity, shear and combined actions, and a wider range of pre-qualified sections, including most sections with longitudinal web and flange stiffeners (based in part on Australian research at the University of Sydney on high strength sections with multiple stiffeners).
Section 8 – Testing has been updated to align with the National Construction Code, which recently underwent changes related to the loading data for wind, snow and earthquake from 50 year to annual probability of occurrence.
According to Hancock, “Two significant changes have been made to Section 8 in the new edition. They are the determination of design values based on prototype testing where the average of the test results can now be used, and calibration of a strength prediction model based on prototype testing.”
“Two significant changes have been made to Section 8 in the new edition. They are the determination of design values based on prototype testing where the average of the test results can now be used, and calibration of a strength prediction model based on prototype testing.”
Professor Greg Hancock, Chair of the Standards Australia Technical Committee responsible for AS/NZS 4600:2018 – Coldformed steel structures.
New sections have also been added to the revised version of the Standard, including Section 9 – Fire, which outlines design requirements for fire protected members at elevated temperatures.
Modular accommodation unit being craned into place on CSU Student Accommodation, a project recently entered into the 2018 Australian Steel Institute’s NSW and ACT Steel Excellence Awards. Image credit: Intelligent Building Systems.
Other new sections include Appendix B – Methods of Structural Analysis (which includes first order, second order and advanced structural analysis based on research at the University of Sydney), and Appendix D – Buckling Stresses. Appendix D now includes requirements for all elastic buckling solutions for local, distortional and flexural-torsional modes to simplify design compared with the previous 2005 edition of AS/NZS 4600 where the buckling equations were scattered through the standard and difficult to follow.
Finally, Section 5.3 – Power Actuated Fasteners (PAFs) now includes requirements for PAFs in tension and shear, and a revised Section 5 – Connections includes new requirements for block shear rupture and net section tension and for screw connections under combined shear and tension.
“Significant research has been performed recently at the University of Wollongong on net section fracture and block shear rupture. New equations have been developed and included in Section 5 – Connections for net section fracture and block shear rupture where new shear lag factors have been incorporated. Further, the shear planes in block shear rupture are now based on average shear planes rather than gross or net sections at bolted connections,” said Hancock.■
Tony Dixon, Chief Executive – ASI
