For decades in Australia, builders and engineers have not been subject to any regulated regime in the selection, design or installation of concrete fasteners and anchors.
Internationally, there have been a number of serious failures of concrete fastening and anchoring systems in construction. This has been due to inadequate selection, design and/or defective installation.
As a response, from 2016 the Australian National Construction Code (NCC) requires job specific tailored engineered concrete fixings/anchors for use with concrete construction.
It is no longer a “buy whatever fasteners are the cheapest without reference to a performance criteria” situation. The NCC is now obligatory and failure to obey may result in prosecutions, significant damages claims and death and/or serious injury.
“Concrete fixings” covers both in-cast and post-installed devices and includes expansion fasteners, chemical fasteners, concrete screw fasteners and undercut fasteners.
Compliance with the NCC is mandatory and the new requirements apply to any “safety critical” concrete construction involving fixings/fastenings.
“Safety critical” is defined as any situation where failure may result in collapse or partial collapse of a structure and/or endangering human life and/or causing considerable economic loss. Design of post-installed and cast-in fastenings for use in concrete is called up by in the NCC and it is based on European Guidelines and product assessment (ETA) which is recognized as best practice around the world.
Pursuant to SA TS 101:2015, safety critical fixings must be designed for a hypothetically “cracked concrete” situation where the load capacity is significantly less than otherwise. Australia does not have a facility currently able to fully test a fixing/anchor for a cracked concrete situation.
It makes sense to design critical fixings if for no other reason than concrete cracking is not considered a defect.
Accordingly, to comply with AS ST 101:2015, the fixing or anchor must be pre-certified to the performance level required (usually European pre-certification) or a brave and technical engineer may specify an alternative solution.
There are a number of trademarked fasteners on the market which, because of the thin locking shell, may well not have sufficient strength specifications to comply with SA TS 101:2015.
Now concrete fixings must be supported with full engineering specifications. This will require engineering analysis, calculations and notation upon engineering drawings. It is no longer acceptable, for example, to have the expression “M-16 Chemical Anchor.” This will add to construction cost, but it is now law, and it is a safety issue which cannot be compromised.
Inferior and low-cost concrete fasteners are problematic, and the relevant engineer must critically assess the performance specifications of such products. Some non-certified fasteners may look almost identical to the pre-certified fasteners, but the cheaper non-certified fastener has been known to be 70 per cent weaker than the pre-assessed and certified product. Such certification is typically labelled/stamped/molded on the fixing.
The three critical elements of concrete fastener/anchor quality assurance are:
- Prequalification – products independently assessed to be fit for purpose
- Design – rigorous assessment to design for critical failure aversion
- Installation – AEFAC trained and qualified installer with experience and/or supervision and compliance with manufacturers specifications.
Concrete fastener suppliers produce and provide free software to assist in design requirements. However, design needs to take account of site conditions and durability objectives.
These changes to the NCC constitute a significant industry change in use of concrete fasteners. The end result will be higher quality, added safety, and therefore a lower risk of failure for both the building professional and the end user/public at large.
At the end of the day, implementing world’s best practice in Australia has to be an engineering outcome that enhances the profile and professionalism of the construction industry as well as making the built environment a safer place for all.