RAPID: Collection of Data on the Performance of Wood Diaphragms in Buildings during the February 2011 Christchurch, New Zealand Earthquake

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

This Rapid Response Research (RAPID) award will collect data to document the performance of unreinforced masonry (URM) construction during the February 2011 Christchurch, New Zealand earthquake. Specifically, this award will document the ability of originally constructed and retrofitted floor and roof diaphragms to efficiently distribute loads to all walls and other lateral-load resisting elements. NZ URM construction from 1880 to about 1970 typically used timber joists, rafters, and trusses, very similar to U.S. construction from the same era. The project will catalog seismic performance at both the qualitative and quantitative levels. At the qualitative level, the project will identify weak or poor detailing typical in URMs and effective mitigating technologies. At the quantitative level, the project will develop guidelines for the type and detailing of retrofit measures to be used in strengthening projects in the United States. These guidelines will be developed in close collaboration with the U.S. masonry industry and practitioners to ensure that results from this research will be transferred quickly to American practice. Building stock in large parts of the United States, including most of the east coast and the Midwest, consists of URM construction. This type of building is known to be very susceptible to collapse under earthquake loading; therefore, effective and economical retrofit techniques are needed to mitigate damage and ensure human safety. The Christchurch event provides unique and exceptional data to calibrate current U.S. practices for seismic evaluation and retrofit of these systems, including retrofits that did not bring the structures to 100% of the strength required by current codes. This latter data is important for the case where seismic retrofits will not be carried as a single project, but rather as a series of smaller projects spread over a number of years as other improvements are made to existing URM buildings. This staged approach has been proposed to spread the cost over a longer period and make the retrofits more feasible. The NZ experience will clarify which vulnerabilities need to be addressed first and which techniques should be used.