22 Jan 2020

Porirua earthquake simulation to help hillside homes

From Checkpoint, 5:45 pm on 22 January 2020

There are hopes an earthquake simulation in Porirua might result in homes being better prepared for a big shake.

The Earthquake Commission said houses on Christchurch's Port Hills suffered more damage than houses in other areas during the Canterbury Earthquakes - even though the ground shaking was roughly the same.

Now EQC and BRANZ, an independent construction consulting company, are trying to find out why.

BRANZ has built wooden platforms on a hilly farm just off the Haywards Hill Rd north of Wellington, each with different foundations.

Swinging weights rock them backwards and forwards - simulating an earthquake.

The idea for the research came after the Canterbury earthquakes of 2010 and 2011 - EQC paid out $10 billion in the aftermath.

EQC resilience strategy and research head Jo Horrock said homes on Port Hills reacted very differently to those on the plains below.

"We learnt from the Canterbury earthquakes that a lot of homes on the slopes on the Port Hills didn't fare so well compared to their counterparts experiencing the same shaking on flat land," she said.

"We wanted to look into this ... find out why they failed ... and what we can do about it in the future."

Quake testing platforms.

Quake testing platforms. Photo: RNZ / Logan Church

BRANZ project lead and structural engineer Roger Shelton said this research was particularly relevant to the Wellington region.

"We have a lot of hills in Wellington, and a lot of this type of [housing] in Wellington and we need to assess how well they will behave, and if possible improve them," he said.

The testing will continue while the weather permits, then BRANZ will take the data it has collected and come up with ways existing foundations can be retrofitted to make them stronger.

"We need solutions the homeowner can get a builder to do easily and cost-effectively," he said.

Roger Shelton

 BRANZ project lead and structural engineer Roger Shelton Photo: RNZ / Logan Church

Horrock said she expected this research might result in changes to building rules.

"We hope that the building code might be changed ... we certainly hope the building industry and the construction industry will build to a higher standard [to the building code]," she said.

"The building code is a minimum life safety requirement - we would like builders to build to a high standard [where] there is less damage in earthquakes and other events."