Performance of the Base-Isolated Christchurch Women's Hospital in the September 4, 2010, Darfield Earthquake and the February 22, 2011, Christchurch Earthquake

Abstract

The Christchurch Women's Hospital, completed in March 2005, is the only base-isolated building in the South Island of New Zealand. The displacement capacity of the base-isolation system and the super-structure ductility capacity are designed to meet 2000-year return-period demands. Detailed structural evaluations after the 2010 Darfield Earthquake and the 2011 Christchurch Earthquake revealed damage only to sacrificial non-structural components at the seismic gaps. Because the structure was not instrumented at the time of these earthquakes, basic design information, ground motion records from nearby sites, and first-hand accounts of the motion in the structure are used to estimate the responses to the main shock and a large after-shock. Results from this modeling effort are used to corroborate reports of structural response from staff present at the time of the main shock and aftershocks. Subsequent instrumentation of the structure is described and will be used to collect aftershock responses for validation of numerical models.

Evaluation of uniaxial contact models for moat wall pounding simulations

“…Excessive isolator deformation can usually be avoided by providing supplemental damping devices, [2][3][4] but under extreme ground motion, the base mat displacement may exceed the provided gap distance and impact the moat wall. 5,6 Moat wall pounding can induce very large accelerations and drift demands, diminishing the effectiveness of the isolation system. [7][8][9][10][11] Figure 1 shows prototypical deformation patterns for three types of buildings: a traditional fixedbased building, a base-isolated building with no impact, and a base-isolated building with impact.…”

Response of hybrid isolation system during a shake table experiment of a full‐scale isolated building

“…Numerous observations of the response of base‐isolated buildings, most with elastomeric bearings (high‐damping rubber, natural rubber, or lead‐rubber), have been made in prior earthquakes (eg,). Although problems with expansion joints have been common, authors have reported that performance and functionality objectives were generally met, and horizontal accelerations recorded at the floor level of instrumented buildings were adequately attenuated relative to the ground acceleration.…”