Building technology stands up to quakes
New Zealand is on the right track with new construction technologies like ‘‘rocking walls’’ to help buildings withstand severe earthquakes, new research reveals.
Researchers from the University of Auckland, University of Canterbury in collaboration with New Zealand research centre QuakeCoRE and the Tongji University in Shanghai, China, built and tested in a laboratory at Tongji University a twostorey concrete-walled building that incorporated the new technologies.
These included post-tensioned ‘‘rocking walls’’, devices that dissipate energy like viscous dampers and lead dampers, and slotted beams.
The building was subjected to intense shaking simulating the types of earthquakes that the capital might experience including a rupture on the Wellington fault and on the offshore Hikurangi fault that would produce long earthquakes.
‘‘We were able to test these different types of earthquakes and prove that under any combination or any type we can actually still get good performance,’’ project leader Dr Rick Henry, a senior lecturer in civil engineering at the University of Auckland and a QuakeCoRE associate investigator, said.
The building had no structural damage and only minor superficial cracks in the concrete after the shaking which was at times greater than the intensity of earthquakes in Christchurch and Kaikoura.
There were only about 10 to 15 buildings in New Zealand with these technologies, Henry said.
Several were in Christchurch and Wellington, one in Nelson and one in Rotorua, and they were two to seven storeys high.
Christchurch’s new library, Turanga, was one of the most significant. Others were the Miles Warren building at Christ’s College and a new building at Southern Cross Hospital.
In Wellington the Royal Society building and the Alan MacDiarmid building at Victoria University featured these technologies.
‘‘Although we are not testing the full height it definitely allows us to understand the system in a way that we can extrapolate that up.
‘‘Christchurch is a really good example in that a lot of what’s been built in the rebuild is the next generation of technology.
‘‘There are a number of timber buildings in Christchurch which use essentially the same idea just with a timber wall instead wall.’’
The project incorporated lowdamage design standards beyond what was required in the building code so that components in the building could dissipate the energy in an earthquake, leaving the structure not only standing but also able to be re-used immediately after.
‘‘So, it is minimising repair and actually avoiding the need to demolish and rebuild again.’’
Henry said the project was taking what engineers had implemented and verifying that they worked and and how they all worked together.
The results should give people confidence in the resilience of new buildings incorporating these technologies, he said.
‘‘I think for us the performance would indicate we’re definitely on the right track and we should keep of a concrete heading in that direction with these types of buildings we have been building.’’
The results showed that the building’s displacement was kept to a minimum.
The damage to the wall base connection where rocking occurred was superficial – minor cracking of concrete – but there was no structural damage.
Cracks in the floor were of a small enough width they were not necessary to repair and had no effect on the building performance.
‘‘So it’s a very positive outcome in terms of proving that the repair is not necessary. I guess the biggest evidence we have for that is that we didn’t just test the building once, we actually tested it about 40 times. We noted that it didn’t need any repair because we just kept testing it again and again.’’