Waking up to the advantages of timber rivets.
They’re ultra strong, and they can save time, and thousands of dollars on a timber build... and timber rivets will soon be easy to incorporate into building design, thanks to the work of a STIC researcher.
Widely used for decades in Canada and North America, timber rivets are hardened steel fasteners that are driven through a rectangular steel plate to form a connection between timber building components. Using timber rivets instead of a conventional system of plates and bolts offers greater strength, with a high load transfer for the connector area, and a stiff connection. The system is quick and easy to install, with no pre-drilling required, bringing labour cost savings. It also allows for adjustments onsite not possible with bolt fastenings.
Timber rivets have just been used for the first time in New Zealand, in the cutting-edge Carterton Events Centre. Built using STIC’s revolutionary EXPAN LVL timber building system, use of the rivets brought superior lateral resistance for earthquake loading, and resulted in a cost saving of $30,000.
Principal Structural Engineer for Opus, and the Structural Design Team Leader for the Carterton project, Dave Dekker, found the timber rivets very user-friendly – both in the workshop and onsite.
“The auditorium trusses in the building were up to 24.6m long and 4.8m high so they were delivered to site in two pieces. The riveted connection uses easily man handle-able components that allowed the required mid-span splice connection to be completed without specialist lifting equipment (other than was required to lift the completed trusses into place) or tools.
“The alternative bolted plate connections were much larger due to bolt spacing requirements in the timber members, and so the compact riveted connections had significantly less visual impact and material cost.”
And the rivets look set to be used more readily here, thanks to the research of Auckland University PhD Student Pouyan Zarnani. Working as part of the Structural Timber Innovation’s R&D programme, Pouyan has based his thesis on establishing a set of design equations to predict wood failures in timber rivet connections.
Pouyan has undertaken an extensive testing regieme, analysing the strength of different connection configuration variables – looking at the numbers of rivet columns, rows, spacing, end and edge distance, and the thickness of the timber member. From this, he has come up with design equations that enable a designer to predict which way the connection will fail, and at what force.
Pouyan’s findings will be available to industry here in coming months, in the form of a short design guide. The guide will eventually become a design clause in the next revision of the New Zealand Timber Design Standard NZS 3603.
And Pouyan’s work has been recognised internationally. He’s been invited to contribute his design equations to the Canadian Design Standard, and asked to present to international researchers at CIBW18 meeting in Sweden this year – a forum looking at leading research, design and analysis methods for wooden structures around the world.
Research Team Leader, Professor of Timber Design and Head of Department of Civil and Environmental Engineering at Auckland University, Pierre Quenneville, says architects and engineers need certainty in design.
“Up to now, they didn’t have that certainty to specify timber rivets. Once the wood failure equation information is available to building designers here in the guidelines, they will be able to specify timber rivets with confidence, and bring their strength and cost benefits to timber buildings in New Zealand.”
In Carterton, the community has welcomed its state-of-the-art new building. Carterton District Council Chief Executive Colin Wright says the use of timber has gone down very well.
“We’ve been able to use the local nature of the timber supply and the fact that it is a natural and sustainable product to good advantage when promoting the centre, and we’ve received a lot of interest around using an innovative timber-based solution for the seismic resistance of the building - just the second time in the world this approach has been used.”
And the community is very proud of its leading-edge facility, says Cultural Services Coordinator Ewan Hyde.
“Our brief was for a natural looking, environmentally sound building – and that’s certainly been achieved, the space has a lot of mana with people here. We often see locals showing people around the centre proudly telling them all about its features.”
The Carterton Events Centre which has used timber rivets.
AT A GLANCE:
Timber rivets are gaining a strong foothold in Australasia have been used for the first time in New Zealand at the Carterton Events Centre building.
They've been widely used overseas for decades.
Timber rivets aid ease of construction and make installation quicker with labour cost savings.
Short Design Guides coming - thanks to work of Auckland University student whose findings are being considered worldwide.