High-rise apartments in earthquake-prone Wellington

By Charlie Dreaver

‘Living the high life on shaky ground’ is a special investigation by RNZ reporter Charlie Dreaver, looking at some of the issues around apartments in earthquake-prone cities.

 

She finds out about the requirements that apartment owners face to strengthen existing multi-owner buildings and bring them up to the new building code, and she visits the University of Canterbury where engineers are working out ways to retrofit safety features to make existing buildings more resilient to large earthquakes.

 

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It was shortly after midnight on the 14th November 2016 and Bede Dwyer was 13 storeys high in his Wellington apartment when the earth began to shake.

 

“I thought ‘oh I’ll just wait this out a little bit, I’m sure it will peter off’, then I heard things smashing in the kitchen and heard the steel beams in the building making a heck of a lot of noise,” he said.

 

Once the shaking stopped Mr Dwyer left his apartment, but the next day he returned for the clean-up.

 

“I was walking through the hallways and people’s front doors were wide open, their lights were on, it was just like an abandoned building,” he said. “It was pretty spooky, especially when the aftershocks were going on and the building was still swaying.

 

“I’m not that keen on apartments anymore, I must say, especially in Wellington.”

 

The challenge of a growing population

 

Despite Mr Dwyer’s reservations about high-rise living following the magnitude 7.8 Kaikōura earthquake, the number of apartment buildings in New Zealand’s cities looks to be on the rise, as more higher-density housing is needed to accommodate growing populations. A recent report, for example, showed that the population of Wellington City is expected to grow by 46,000 to 74,000 residents by 2047.

 

Wellington City Council‘s chief resilience officer Mike Mendonca said that juggling a city at risk of large earthquakes and a growing population was a major challenge.

 

“We know we are going to grow whether we like it or not, [and] we know we have earthquakes,” said Mr Mendonca. “What that means is we need to make trade-offs. And it means we need to understand what the risks are and do better to mitigate those risks when people come to live in our city.”

 

Mr Mendonca said new buildings are easier to make earthquake resilient than pre-existing buildings.

 

“We are already seeing the first apartment building in Wellington that is base isolated and increasingly that’s what the market is expecting,” he said. “We are really happy about that, [that] most of the new buildings in Wellington are base isolated or have dampers.”

 

However, Mr Mendonca said retrofitting existing buildings is much tougher and it’s much more stressful on those who own and occupy them.

 

The Building (Earthquake-prone Buildings) Amendment Act 2016 introduced major changes to the way existing earthquake-prone buildings are identified and managed.

 

Multi-storey buildings have had to be rated on how earthquake prone they are and the owners have been given a time frame in which to bring them up to a new building code standard.

 

For apartment owners looking to repair earthquake damage, EQC’s head of claims David Ashe said multi-owner apartment buildings can add an extra layer of complexity.

 

Earthquake strengthening an expensive business

 

Lesley Hamilton, who lives on Cuba Street, says she is looking at a bill of around quarter of a million dollars to get her apartment strengthened to meet the new building code.

 

Ms Hamilton said other residents in the same building who don’t have the equity to borrow enough money to earthquake strengthen will have no other choice but to sell their apartments at a much lower cost than they bought them for, putting many people in financial hardship.

 

She would like to see more financial assistance from local or central government available to help apartment owners strengthen their buildings to the new building code.

 

“We bought in good faith,” she said, but “they changed the rules. They need to give us more help.”

 

New fund to help apartment owners

 

Local Wellington Central MP Grant Robertson said a new $23-million hardship fund is being developed for apartment owners, but it wouldn’t be available to everyone.

 

“It’s a fund to fund people who just can’t bring the finance together or where it would put them under undue hardship,” he said. “That fund is being organised as we speak, and we are very hopeful by the end of the year we can begin taking applications for it.”

 

It is not known how many people might apply for the fund and Mr Robertson didn’t rule out the funding needing a top-up.

 

Engineering more earthquake-resilient apartment buildings

 

University of Canterbury’s Director of Studies for Earthquake Engineering, Associate Professor Tim Sullivan, said work is underway in the university’s engineering laboratories to find cost effective ways to reduce damage and safety risks in pre-existing buildings.

 

Their research focus at the moment is on precast concrete flooring.

 

Prof Sullivan said that during an earthquake “one of the issues with the pre-cast flooring is that as the building deforms there is quite a brittle element.

 

One solution the researchers are looking at is a catch-frame system below existing flooring units, so that if they fall they are caught by something acting as a safety net.

 

The university’s engineering labs contain a large shake table, that is used to simulate earthquakes of different magnitude and acceleration.

 

PhD candidate Muhammad Rashid has surveyed sprinkler systems at hospitals, apartment buildings and malls.

 

“We are testing these sprinkler systems to different levels of acceleration and then we will see the performance of these systems at different shaking levels.”

 

Professor of Structural and Earthquake Engineering, Rajesh Dhakel, stressed the importance of testing individual components of a building.

 

“If we test the whole building … and if something doesn’t go well, it will be very difficult to pinpoint what is the cause of the failure or what didn’t work, because there are interactions between different components,” he said.

 

He said non-structural elements, such as ceiling panels for example, are also crucial for the functionality of the building after a large seismic event, especially as the expectations for buildings were changing.

 

“We now know if things are done according to the modern [building] code we can more or less assure life safety, but still people are not happy.”

 

He said the last Canterbury earthquake sequence caused more than $40 billion in damage, much of that to buildings that required repairs and in some cases demolition and rebuilding.

 

“That is huge money, so how does the country sustain that or [could] that be avoided? That’s the question being asked,” said Prof Dhakel.

 

This story was made possible through the Aotearoa New Zealand Science Journalism Fund

High-rise apartments in earthquake-prone Wellington
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