EAGER: Instrumentation and Modeling of Seismic Isolation in Aftershocks

Duke University, Durham NC

Investigators

Abstract

The research objective of this project is to measure the long-term seismic responses of the base-isolated Christchurch Women's Hospital, located in Christchurch, New Zealand, and to use these measurements, along with computational models, to assess the relative effects of soil-foundation-structure interactions with liquefying soil, for interactions between adjacent buildings, and for interactions across the isolation interface. Nine networked triaxial accelerometers and three displacement sensors, installed at three levels within the structure, will allow for remote monitoring of aftershock responses and rapid data processing. The database of high fidelity measurements from this building will be combined with detailed computer simulations of the structure, isolation system, foundation, and supporting soft soil. The project team, including researchers in structural and geotechnical engineering at the University of Canterbury, Christchurch, New Zealand, engineers from firms in New Zealand conducting geotechnical field investigations at the building site, and hospital staff, will collaborate on the deployment and remote monitoring of the instrumentation, the development and application of modern system identification techniques to the data, and the development of nonlinear numerical models to examine the processes governing the response of this structure. Vibration measurements obtained in situ from buildings during actual earthquakes are invaluable in assessing and improving the performance of earthquake protection systems. Following the large earthquakes of 2010 and 2011, Christchurch has experienced, and continues to withstand, hundreds of earthquake aftershocks per year. This project seizes the unique opportunity to capture perishable data from the seismically-isolated Christchurch Women's Hospital, a building designed to be particularly earthquake-resistant. While this facility is providing uninterrupted service throughout this sequence of earthquakes, some aspects of the dynamic response of this structure are unanticipated. By combining measurement and analysis, researchers will identify the aspects of this structure leading to the measured and observed motions. These results will bear on the design of new base-isolated structures on soft soils in Christchurch, New Zealand and in other seismic regions worldwide. Knowledge gained from this project will contribute to best practices for the implementation of seismic isolation systems. Data obtained from this project will be archived and made publicly available in the NEEShub Project Warehouse (http://nees.org/warehouse).