EXPECTATION MEETS REALITY: SEISMIC PERFORMANCE OF POST- TENSIONED PRECAST CONCRETE SOUTHERN CROSS ENDOSCOPY BUILDING DURING THE 22 ND FEB 2011 CHRISTCHURCH EARTHQUAKE

The 22 nd Feb 2011 Christchurch earthquake highlighted the mismatch between the expectations of building occupants and owners over the reality of engineered buildings‟ seismic performance. Ductile plastic hinging behaviour of conventional reinforced concrete (RC) structures in large seismic event such as those of 22 nd Feb are expected by structural engineers. However, the reality of months of downtime and loss of occupancy of the building is not expected or desired by building users and owners. The innovative PRESSS-technology, utilising un-bonded post-tensioning precast concrete elements to achieve re-centering behaviour, is a new approach to achieve low damage seismic performance, in which building functional downtime and required structural repair are minimised. The Southern Cross Hospital Endoscopy building is the first application of the innovative PRESSS design technology in the South Island of New Zealand. The structure consists of four post-tensioned precast concrete frames in the North-South elevation and two sets of post-tensioned coupled precast concrete walls in the East-West elevation. Structex Ltd, in collaboration with the University of Canterbury and Fletcher Construction, delivers the five-storey Warren & Mahoney-designed building with a lower construction cost, reduced construction period and significantly improved seismic performance. The seismic performance of the Southern Cross Hospital Endoscopy building during the 22 nd Feb Christchurch earthquake suggests that the expectation of clients can be met by innovative structural solution. In addition to reporting on the details of the structural design and its performance during the 22 nd Feb event, the paper demonstrates the use of non-linear numerical model as a design verification and post-earthquake assessment tool.