Quake-testing the whole building
New Zealanders can be more confident that new buildings built in New Zealand can stand up to earthquakes of a greater intensity than those that recently hit Christchurch and Kaikoura, say University of Auckland engineers.
This is according to the findings of researchers from the University of Auckland and Canterbury, in collaboration with QuakeCoRE and Tongji University, China. They built a two-story concrete building (10m x 6m x 8m), put it on one of the largest shake tables in the world, and subjected it to the same seismic demands that could shake New Zealand.
“It’s the most exciting project I’ve completed in my career so far,” says University of Auckland Senior Lecturer in Civil and Environmental Engineering, Dr Rick Henry, who led the project.
As he notes, China is one of only a few countries in the world that have shaking tables of this size. “It’s the largest and most complex test I’ve ever done, on a much larger scale than we would ever be able to achieve in New Zealand.”
Generally engineers design buildings to resist earthquakes based on numerical models and design standards that have been validated by testing individual components of buildings such as a wall or a beam.
A test of this scale allowed the researchers to evaluate the building as an integrated whole, a complete system rather than parts of a system, with the entire structure subjected to real earthquake ground motions.
“Tests of this scale are extremely valuable and the data you can gather from what is a quick test but on a large scale, and what you can learn from it, is huge.”
The team conducted around 40 tests, subjecting the building to the forces that characterise the different types of earthquakes that have affected New Zealand, such as the sudden, intense earthquake generated by the Wellington fault line, or the long-duration subduction earthquake generated by a rupture off the East coast of New Zealand.
The latest testing started at low intensity and gradually increased, from the kind of earthquake that might occur every 25 years, to an earthquake of an intensity that might occur every 2500 years.
The results suggested that buildings built according to contemporary design knowledge in these shaky isles have a robust future ahead of them.
“The test provided confirmation that current state-of-art design practice will perform exceptionally well in an earthquake,” says Dr Henry. “All of the details we used were based on existing buildings constructed in Wellington and Christchurch and showed excellent performance.”
Watch the video of a two-story building being rattled by one of the world’s largest shake tables.