Application of Energy Dissipation Devices for Seismic Protection of Soft-Story Wood-Frame Buildings in Accordance with FEMA Guidelines

Abstract

Recent earthquakes have demonstrated the vulnerability of soft-story wood buildings. A performance-based retrofit option focusing on stiffening/strengthening only the soft ground story, as regulated by FEMA guidelines, was proposed in an attempt to achieve collapse prevention of the ground story while at the same time ensuring damage control of the upper stories. This paper focuses on an alternative retrofit approach that focuses on energy dissipation, in order to achieve a performance that is essentially comparable to the inherent performance target defined in FEMA guidelines. A viscous damper retrofit is designed based on conclusions drawn from parametric studies. Then, the proposed retrofit is validated via slow pseudodynamic hybrid testing of a full-scale three-story building. The test data are presented, interpreted, and compared against both pretest numerical predictions and posttest simulation results after model calibration. It is demonstrated that a damping retrofit, as compared to a stiffening/strengthening retrofit, better complies with the FEMA retrofit standards due to its effectiveness in reducing ground-story peak deformations while being less likely to propagate damage to the upper stories.