Evaluation of response modification factor for steel structures with soft story retrofitted by viscous damper device

Abstract

The soft story located in the basement of tall buildings for parking or shopping lot. Considering the limitation in architecture, these structures may be retrofitted by implementing earthquake energy dissipation such as viscous damper devices in soft story level. Nevertheless, an extensive review of related literature indicates that the effect of viscous damper on response modification factor is not considered. Therefore, this study proposed the response modification factors for steel structures furnished with viscous damper devices in soft story level and investigated the effect of implementing such devices on the response modification factor. In this research, steel structures with numerous stories were considered to evaluate the response modification factor, which was formulated based on three aspects, namely, strength, ductility, and redundancy factors. Quasi-static nonlinear analysis was performed using finite element software based on structural models equipped with damper devices installed in different locations of the parking level. No open bay is available in other floors to install the damper devices. Meanwhile, the overstrength, ductility, and response modification factors were established by conducting pushover analysis. Results of the study revealed that the response modification factors for structures equipped with damper devices are higher than those of structures without damper devices. Moreover, the value of response modification factor was affected by the number of stories and number of dampers. Considering the analytical results for different cases, the equation for determining the response modification factor for steel structures furnished by viscous damper devices in soft story level was proposed.