Seismic vulnerability church study queried

A Dunedin structural engineer and church leader has questioned why international seismologists and engineers are analysing up to 29 Dunedin churches to gauge their seismic fitness in the event of an earthquake.

The two-year project, funded by the Earthquake Commission, will involve scientists from New Zealand, Italy and Portugal developing a seismic vulnerability index for unreinforced masonry churches and historic buildings to help with decisions on retro-fitting to prevent damage in future earthquakes.

However, St Paul's Anglican Cathedral vestry and works committee, and Opus Dunedin earthquake risk management and strengthening consultant Thomas Moore had several concerns about the research.

While he welcomed the funding of the international study to explore rationally the seismic vulnerabilities of Dunedin's heritage churches, he asked the research group to focus closely on the practical issues of seismic upgrading by presenting a library of construction details acceptable to the New Zealand Historic Places Trust, rather than merely running a scoring system.

Dr Moore said the New Zealand Society of Earthquake Engineers (NZSEE) recently upgraded the initial evaluation procedure (IEP) to give substantial credit for previous strengthening work, such as that performed at St Paul's in 1968 when a new apse was constructed, enlarging the cathedral substantially, with new reinforced structural elements.

Under the IEP scoring system adopted in 2014, the work improved the seismic capacity of the cathedral significantly, he said.

''We would like to know if the new study will replace the 2014 scoring system.

''St Paul's is required to present an engineering evaluation of the cathedral by July 31, 2014.

''It is unlikely that the new scoring system will be in place by this date.

''Perhaps the real challenge is to design affordable strengthening measures or stiffening measures that limit building displacements, instead of focusing on another scoring system,'' he said.

A spokesperson for the research group could not be contacted yesterday for comment.

St Paul's Cathedral is one of 29 unreinforced churches that are being analysed in Dunedin, under the project ''Vulnerability Analysis of Unreinforced Churches in New Zealand''.

Project leaders have emphasised the churches in their study were being analysed because they were unreinforced masonry churches, which are usually the most seismically vulnerable buildings, but it did not mean they were unsafe.

It only meant scientists were trying to assess their vulnerability to find out the type of damage that could be expected in an earthquake.

Timber churches are usually less vulnerable to earthquakes, and the main focus of this project was to scrutinise unreinforced brick and stone churches throughout New Zealand.


Under scrutiny
The Dunedin churches involved in the study are.-
Knox Church, St Paul's Cathedral, Sacred Heart Church, Glenhaven Church, First Church of Otago, St Michael's Anglican Church, Gospel Chapel Mosgiel, Caversham Presbyterian Church, St Mary's Catholic Parish, The Salvation Army NZ Trust, Mosgiel Presbyterian Church, North Taieri Presbyterian Church, Kaikorai Presbyterian Church, Halfway Bush Union Church, Andersons Bay Presbyterian Church, St Mary's Anglican Church, Baptist Union of New Zealand, Northeast Valley Presbyterian Church, All Saints' Anglican Church, St Clair Presbyterian Church, St Patrick's Basilica, St Bernadette's, St Peter's Church, St Joseph's Cathedral, New Zealand Methodist Church, Holy Cross Church, St Mary Star of the Seas, Holy Trinity Church, and South Dunedin Presbyterian Church.


- john.lewis@odt.co.nz

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