Friction device may hold key to quake-proofing buildings
With a construction boom imminent in Canterbury, a Unitec civil engineering lecturer is involved in cutting-edge research which could lead to “damage-resistant” timber buildings in earthquake-prone areas.
Wei Loo, from the Faculty of Technology and Built Environment, is in the next phase of his research on a friction device that would allow timber walls to lift and tilt in a controlled manner during an earthquake, and then self-right.
In theory, the system will not only prevent the building from collapsing, but would let the structure come back to its original position with negligible damage.
Wei undertook this research for his masters thesis at the University of Auckland before the earthquakes hit Christchurch last year, and is now continuing it for his PhD.
In the wake of the devastation, experts led by the Royal Society of New Zealand recommended the use of timber walls and other “earthquake-friendly” materials to improve building safety standards, which attests to the relevancy of the research Wei is currently undertaking.
As well as using timber walls, installing specially designed steel friction plates is crucial to Wei’s research.
Wei says his system allows some play at the point where the wall connects to the concrete foundations, allowing steel plates to slide relative to each other.
This would allow the shear walls — those parts of a building engineered to withstand horizontal wind and earthquake forces — to rock and tilt rather than bend and snap.
“So under a strong earthquake event, the plates are going to slide,” Wei says.
“This will allow some uplift of the wall at its base. The other great thing is that when the plates move backwards and forwards they will give off heat and dissipate the energy through the plates rather than through the wall, which will also help avoid excess damage to the wall.
“And apart from a bit of scratching, the plates won’t be damaged much either. That’s the aim of the research.”
How those shear walls then connect to other walls and to the roof structure is the subject of ongoing research.
Already, computer modelling of the shear wall has had promising results. The next step is to design the actual connector and then attach it to the shear walls and test the system in simulated earthquake conditions.
The idea of sliding or rocking timber walls is not a new one. Since the late 1960s New Zealand engineers have been using building design approaches based on such a “controlled structural yielding”, according to a report from the Royal Society of New Zealand.
But Wei hopes his device will provide an economically viable alternative to current designs, and help promote more and better use of sustainable and eco-friendly timber for building construction.
In keeping with Unitec’s commitment to supporting applied research that delivers value and impact for its community, stakeholders and industry, Wei says that once the research is done and the results are shown to have good potential, it will be provided to the industry for implementation.