Seismic Assessment of Buildings, Considering Post-Earthquake Safety

Advanced Seismic Assessment Guidelines, developed by researchers at Stanford University and tested by practicing structural engineers, offer improvement over previous methods for seismic evaluation of buildings where post-earthquake safety is a concern. This new method allows engineers to evaluate, before an earthquake, how safe it will be to occupy a building after the earthquake. The method measures building performance in terms of the post-earthquake occupancy classifications "Green Tag," "Yellow Tag," and "Red Tag," defining these performance levels quantitatively, based on the structure's remaining capacity to withstand aftershocks. The authors have used this methodology to perform seismic assessments for several buildings in the Pacific Gas & Electric Company (PG&E) utility network, including electrical substations and other facilities in Oakland, Berkeley, San Francisco, and Vacaville. Analytical and probabilistic features of the method are also applicable to more typical seismic evaluation and retrofit projects, where evaluation of post-earthquake occupancy tagging is not needed.