Substantial changes to concrete industry ‘bible’

On its completion in 1910, Auckland's Grafton Bridge was the world's largest span-reinforced concrete arch bridge. It took over two and a half years to complete.

On its completion in 1910, Auckland’s Grafton Bridge was the world’s largest span-reinforced concrete arch bridge. It took over two and a half years to complete.

Representatives from the New Zealand Concrete Society (NZCS) have had significant input into amendments to the New Zealand Concrete Structures Standard (NZS3101) primarily intended to address recommendations from the Canterbury Earthquakes Royal Commission.

“Work on this important Standard has been ongoing for the last couple of years and is in the final stages of development. It is essentially the concrete industry bible,” says Allan Bluett, secretary/manager of NZCS.

Richard Henry, NZCS member and senior lecturer at the Department of Civil and Environmental Engineering at University of Auckland worked on the Standards committee and says there have been significant changes to a number of sections.

“The key amendments relate to deformation compatibility, precast floor unit seating, and wall design. Explicit consideration of axial elongation is now required as well as total deformation demands during a maximum considered earthquake for components such as floors, cladding panels, and stairs.”

He says the extensive research into precast concrete floor systems has resulted in further revision to the support connection detailing.

“Amendments to the structural walls chapter (Chapter 11) are extensive, with significant changes as a result of the observed performance of concrete walls in Christchurch.  The minimum vertical reinforcement requirements have been rewritten, limitations placed on the use of singly reinforced walls, refinement of transverse reinforcement detailing, addition of axial load limits, and provisions for the overstrength of coupled wall systems.”

A number of design issues with concrete walls are still the subject of ongoing research and additional amendments are expected in future revisions to NZS 3101, he says.

“All of these changes are expected to improve the robustness of reinforced concrete buildings and make them safer during earthquakes.”

Allan Bluett says New Zealand is recognised as a world leader in seismic concrete construction due to the work of some ‘very clever professors’ (Park, Paulay and Priestly), in the 1970s.

Until 1980, NZCS was known as the New Zealand Prestressed Concrete Institute, which was incorporated in 1964

For the last 52 years, under both guises, the Society has encouraged a greater knowledge and understanding of all aspects of structural and architectural concrete, says Allan.

“As a learned society we work closely with universities in the development of new construction methods and uses for concrete.  We have always taken great pains not to have a commercial bent but to remain focused on the technical side of the industry, encouraging new technologies and facilitating training, as well as contributing to the development of Codes and Standards.”

He says the organisation came into existence in response to steel shortages in the years following the Second World War.

“Precast concrete was just being developed and going ahead in France, but the whole industry sector in New Zealand was controlled by the Ministry of Works, which was loathe to look at new technologies. The Institute was formed to essentially convince MOW to consider precast concrete.”

Allan says more information about the ‘fascinating history’ of the Society and concrete sector can be found in the History and Heritage section of the NZCS website, concretesociety.org.nz which includes a 10 minute video looking at post war construction in New Zealand.

Today, NZCS also facilitates the New Zealand Concrete Industry Conference and bi-annual awards, which recognise excellence in concrete construction.

This year’s event is being held from 6 to 8 October at the Ellerslie Event Centre in Auckland, where keynote speakers include Professor Joost Walraven from the Technical University of Delft, who is an expert in many aspects on concrete technology and structural applications, with his recent work focused specifically on the development of new types of concrete and their application.

Professor Ken Elwood, who serves as the MBIE Chair in Earthquake Engineering and Director of the newest Centre of Research Excellence (CoRE), QuakeCoRE: Centre for Earthquake Resilience, will present on his post-earthquake residual capacity research.

“We are looking forward to another great conference. The scale of the venue at Ellerslie enables our trade exhibitors to exhibit some heavy equipment, including live demonstrations. Interest is already very high and we are hopeful of attracting close to 400 plus delegates,” says Allan.

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