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Britomart Transport Interchange, Auckland: Alterations and strengthening of the former Chief Post Office

E.T. Sainsbury and M. Gibbs

This paper outlines the structural alterations undertaken to transform the former Auckland Chief Post Office into the Britomart Station Interchange main entrance and ticket hall, including strengthening of the existing building, enclosure of the existing lightwell, the addition of a large steel framed “glasshouse” atrium, and lowering of the ground floor.

The building is relatively large, being 52m x 42m in plan and four storeys high, plus a basement. It was built in 1910 with an internal gravity resisting steel frame, it originally used the brick walls to resist lateral loads, but with the unreinforced 18m high facades and a soft storey effect at the internal atrium, it did not comply with the New Zealand Building Code.

Strengthening involved the addition of reinforced concrete shear walls on the inside of the perimeter walls and the creation of a well connected diaphragm at each floor level.

As it occupies a prominent site at the foot of Queen Street, and has Auckland City Council Heritage classification, strengthening and incorporation into the station complex seemed natural. Britomart Station, which is below the CPO, has been described in earlier papers. (Fig 1).

Paper P26: [Read]

Prediction of beam elongation in structural concrete members using a rainflow method

J.G. Matthews, J.B. Mander and D.K. Bull

The prediction of beam elongation has been studied by various researchers. Results have shown that beam elongation can be predicted by assuming that the elongation varies proportionally with interstorey drift. A Rainflow Counting method is proposed that enables a better understanding of how beam elongation occurs. The method predicts the amount of beam elongation on an individual plastic hinge basis or a frame as a whole. This predictive approach is then validated against the results conducted as part of a current research programme.

Paper P27: [Read]

Estimated losses due to post-earthquake fire in three New Zealand cities

W.J. Cousins

Property losses due to earthquake shaking and post-earthquake fire are estimated for three urban areas in New Zealand, i.e. Wellington City, Napier/Hastings and Dunedin. Wellington dominates the losses for both shaking and post-earthquake fire. For any given return period, the shaking losses for Wellington are estimated to be about 5 times larger than those for Napier/Hastings which in turn are about 5 times larger than those for Dunedin. The relative importance of the fire loss depends on the return period. For return periods of up to about 800 years the loss due to post-earthquake fire in Wellington is expected to be much smaller than the loss due to shaking. For a return period of about 1200 years the two losses are equal, and for return periods of 2000 years and more the fire loss greatly exceeds the shaking loss. For Napier/Hastings the fire loss equals the shaking loss at a return period of about 4000 years, and for Dunedin the fire losses are much smaller than losses due to earthquake shaking for return periods up to 100,000 years. The probabilistic method used for estimating the losses, and limitations in the modelling, are described.

Paper P28: [Read]

Towards a first-order earthquake loss model for New Zealand

W.J. Cousins

A simple earthquake loss model for New Zealand buildings and people is outlined. It provides prompt (i.e. within seconds) first-order estimates of losses and casualties from scenario earthquakes. For major earthquakes affecting urban areas its accuracy is sufficient to answer the question “are there likely to be 1, 10, 100 or 1000 casualties, and is the damage expected to be 1, 10, 100 or 1000 million dollars”.

Paper P29: [Read]

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