Damage Index for Soft-Story Wood Frame Buildings

Past research has shown that soft-story wood frame buildings are vulnerable to seismic damage and potentially collapse in high intensity events. For seismic resilience assessment of these structures, it is essential to classify damage states after an earthquake. This paper describes the formulation of a damage index (DI) for post-earthquake assessment of wood frame buildings with a soft and weak first story. The indices are applied to a wood frame building representative of buildings built prior to 1970 in California and the United States in general. Data from shake table tests of a four-story full-scale model building is used for correlating specific structural parameters with associated damage identifiers. The model building was subjected to ground motions with increasing intensities, and it experienced different levels of damage. The computed DI is used to define different damage states on global as well as component levels. The proposed framework is found useful for the determination of a wood building’s suitability for occupancy after a major seismic event.