Revisions to the Australian Standard AS/NZS 1252 have raised the bar in relation to the integrity of structural bolt assemblies.
In 2003, a bolt no more than five centimetres long contributed to the most expensive construction accident ever witnessed in Canberra.
The collapse of the hangar at RAAF Base Fairbairn was found to have been caused in part by poor-quality bolts that failed when tested to Australian Standards. Bolts recovered from the hangar showed that many had split in two, while others had deformed significantly under load. Twelve workers were seriously injured in the incident.
The hangar collapse was a wake-up call to the construction industry about the use of building products that don’t comply with Australian Standards. But, a decade on, doubts continued to be expressed about the use of non-conforming building products (NCBPs) on Australian construction sites.
In a 2013 report entitled The quest for a level playing field: the non-conforming building products dilemma, the Ai Group raised serious concerns about the effectiveness of Australia’s approach to ensuring the quality and safety of building and construction products. The report had its seed in a growing body of anecdotal reports by businesses about the use of NCBPs, in addition to clear instances of product failure such as at RAAF Fairbairn. It also had as its backdrop the growth of new centres of global product supply and the greater penetration of imports into the Australian construction sector.
The Ai Group surveyed 222 companies and found that 92 per cent reported non-conforming product in their market. Among the inadequacies found in building and construction performance, the report revealed failings in surveillance, audit checks, first-party certification, testing and enforcement.
Bolts in construction
Revisions to the High Strength Bolting Standard AS/NZS 1252 Parts 1 and 2 published in December 2016 go a long way to redressing concerns about the use of non-compliant bolts by the construction sector.
Part 1 of the revised Standard provides an updated definition of product conformity to ensure high-strength steel bolt assemblies in steelwork construction are consistent with Australian Standard AS 4100. It includes a new definition of the functional requirements of bolt assemblies as distinct from the separate components, as well as a mandatory bolt assembly test.
Part 2 of the Standard is an entirely new section and defines the requirements for a range of testing that can be undertaken to verify product conformity to AS/NZS 1252 Part 1. In the context of an increasingly globalised procurement regime, Part 2: Verification Testing has an important role to play in ensuring the quality of all high-strength bolts imported into the country.
Dr Peter Key, National Technical Manager at the Australian Steel Institute (ASI), says it’s the responsibility of everyone in the Australian steel industry involved with bolted connections to support Part 2 of the Standard.
“Knowing the issues with non-compliant product, particularly high-strength bolts, can you really justify your ‘Duty of Care’ under WHS Regulation if you choose not to specify verification to Part 2 of AS/NZS 1252?” he asks.
“Independent verification is the only objective way to ensure that these crucial connections are up to specification to stated structural requirements and confirm the commitment to safe structures that minimise risk during construction and for the design life of the structures.”
Key’s advice to procurers is to specify verification testing to AS/NZS 1252: Part 2 even if it means bolt assemblies costing extra. Procurement will still be cost-competitive and verification testing will ensure high-strength bolt assemblies meet the expectations of the community.
Arun Syam, Business Development Manager at OneSteel, said that Australian Standards relating to bolts have been a weak link in the past, but that the revised Standard will help improve expectations across the sector.
“The steel industry aims to engender confidence in steel solutions. The revised AS/NZS 1252 series of Australian Standards will have the effect of increasing confidence in using steel products,” he said.
The ASI has made available a revised Technical Note on high-strength structural bolt assemblies for download from: http://steel.org.au/elibrary/asi-technical-notes/