Seismic assessment

DETAILED SEISMIC ASSESSMENT

Beca were commissioned by Rotorua Lakes Council (RLC) to undertake a Detailed Seismic Assessment (DSA) of the Sir Howard Morrison Performing Arts Centre.

Following their extensive investigations, their final assessment rated the building at 25% of New Building Standard (NBS), meaning the building is considered earthquake prone.

It was closed to the public in November 2017.

BUILDING IMPORTANCE LEVEL

Before closing, the Sir Howard Morrison Performing Arts Centre was hosting more than 44,000 visitors each year.

Because of it high level of public use, it has an Importance Level 3 (IL3) building classification. This means that in the event of a failure there is considered to be high consequence for loss of human life, or very great economic, social or environmental impact.

ASSESSED SEISMIC RATINGS

The results of the Detailed Seismic Assessment (DSA) indicate the building’s seismic rating to be 25% NBS (IL3).

This minimum rating is applied to the whole building, but is governed from the lowest rating of 25% NBS (IL3) in the supper room, fly tower and Foyer. The Concert Chamber is rated at 30% NBS (IL3), the Civic Theatre auditorium is rated at 50% NBS (IL3) and the Banquet Room is rated at 90% NBS (IL3).

The out of plane, unreinforced pumice block walls are one of the major limiting factors for building capacity. Buckling of foyer truss bottom chords due to geotechnical movements, buckling of Concert Hall props, and deficient connections in the fly tower also contribute to capacities below 34%NBS.

EARTHQUAKE PRONE STATUS

Buildings with an NBS rating of more than 34% but less than 67% NBS are considered to be ‘Earthquake Risk’ buildings.

Buildings with a seismic rating less than 34% NBS are considered to be Earthquake Prone, and under the Building Act must be either demolished or strengthened.

With a rating of just 25% NBS (IL3) the Sir Howard Morrison Centre is therefore categorised as Earthquake Prone.