Quake study sets out safety steps
A report into the 80 Wellington buildings identified for intensive earthquake testing has come up with nine recommendations to make the city safer.
The report, by crisis management firm Kestrel Group, was released by Wellington City Council yesterday, with mayor Justin Lester saying that it would enable building owners, engineers and government agencies to refine current standards and make improvements.
The main recommendations relate to ground and soil conditions across Wellington, and the need for ‘‘urgent’’ experimental testing of damaged precast floors.
The 80 buildings were chosen because they shared similar characteristics to Statistics House, on Wellington’s waterfront, which partially collapsed in November’s Kaikoura earthquake.
Those shared characteristics were that the buildings were four to 15 floors high; each had a reinforced concrete structure, particularly with precast floors; and they were all built on soft soils with flexible design.
In February, Lester said the results of invasive tests on most of the 80 buildings had uncovered some damage but no threat to public safety.
The Kestrel report found a correlation between the buildings and the soil or ground conditions beneath them. An earlier Ministry of Business, Innovation and Employment (Mbie) report into the failure of Statistics House found a similar correlation.
Kestrel calls for better definition of ground conditions across Wellington for the purposes of both seismic assessment and design, and to enable better estimation of seismic demands on buildings after a quake.
It says experimental testing of damaged precast floors is urgently required, as are industry-agreed performance objectives.
Meanwhile, the engineering sector is urgently working on technical solutions to retrofit, repair and strengthen buildings with precast floors, and on how to address seismic rating variability.
Wellington City Council resilience manager Mike Mendonca said buildings with significant issues were either closed for further assessments or repair, and strengthening work was under way.
The council plans to review and improve the way it gathers, interprets and acts on the information available after an earthquake, which includes a plan to install earthquake-measuring devices in 400 Wellington buildings. It is considering options as part of the annual plan process to improve the sensor networks across the city.
MBIE deputy chief engineer Dave McGuigan said there were national lessons be learned from what happened in Wellington after the Kaikoura earthquake, and authorities would work with other earthquake-struck cities such as Los Angeles, and Kobe in Japan.
McGuigan said almost $190,000 had been given to the earthquake resilience research group QuakeCore to study precast floors to better understand their seismic performance.
Sizing up the performance of precast floors in flexible buildings would also be investigated, with the aim of retrofitting the floors to make them stronger.
Wellington engineer and property developer Maurice Clark said there were no surprises in the Kestrel report. Most engineers in the city were aware of the issues outlined, as well as the recommendations and expectations.
Property developer Ian Cassels said Wellington should be New Zealand’s version of Tokyo. ‘‘With the right management, this city can easily defend itself against a big earthquake.’’
It needed a new philosophy about how its buildings worked, and owners needed to be technically aware.