Formulation of Seismic Fragilities for a Wood-Frame Building Based on Visually Determined Damage Indexes

Abstract

The study of earthquake engineering has made significant strides over the last one-half century with scientists developing methods to better understand the basis and mechanisms of earthquakes and engineers working to mitigate economic loss and fatalities. A paradigm known as performance-based seismic design (PBSD) not only provides life safety to building occupants, but seeks to control structural and nonstructural damage in buildings and other structures. The development of fragility curves based on the well-known Park-Ang damage index is examined herein. This type of formulation can provide the information needed to assess the seismic vulnerability of a structure. Existing shake table test data from the NEESWood Project’s test of a 223 m2 (1,800 sq ft) two-story house was combined with a participant survey to calibrate a damage model. The result was the development of damage fragilities based exclusively on nonlinear time history analysis. Then, the proposed numerical damage model was applied and fragility curves were developed for a six-story light-frame wood condominium building. The results appear logical based on observations of system-level shake table tests over the last decade, and thus the method shows promise provided significant torsion is not present in the system.