Base isolation of New Zealand light-frame wood buildings.

Research papers, University of Canterbury Library

Base isolation is an incredibly effective technology used in seismic regions throughout the world to limit structural damage and maintain building function, even after severe earthquakes. However, it has so far been underutilised in light-frame wood construction due to perceived cost issues and technical problems, such as a susceptibility to movement under strong wind loads. Light-frame wood buildings make up the majority of residential construction in New Zealand and sustained significant damage during the 2010-2011 Canterbury earthquake sequence, yet the design philosophy has remained largely unchanged for years due to proven life-safety performance. Recently however, with the advent of performance based earthquake engineering, there has been a renewed focus on performance factors such as monetary loss that has driven a want for higher performing residential buildings. This research develops a low-cost approach for the base isolation of light-frame wood buildings using a flat-sliding friction base isolation system, which addresses the perceived cost and technical issues, and verifies the seismic performance through physical testing on the shake table at the University of Canterbury. Results demonstrate excellent seismic performance with no structural damage reported despite a large number of high-intensity earthquake simulations. Numerical models are subsequently developed and calibrated to New Zealand light-frame wood building construction approaches using state-of-the-art wood modelling software, Timber3D. The model is used to accurately predict both superstructure drift and acceleration demand parameters of fixed-base testing undertaken after the base isolation testing programme is completed. The model development allows detailed cost analyses to be undertaken within the performance based earthquake engineering framework that highlights the monetary benefits of using base isolation. Cost assessments indicate the base isolation system is only 6.4% more compared to the traditional fixed-base system. Finally, a design procedure is recommended for base isolated light-frame wood buildings that is founded on the displacement based design (DBD) approach used in the United States and New Zealand. Nonlinear analyses are used to verify the DBD method which indicate its suitability.