Probabilistic residual drift assessment of SMRFs with linear and nonlinear viscous dampers

Maximum Residual Interstory Drift Ratio (MRIDR) is one of the most important Engineering Demand Parameters (EDPs) for evaluating the safety of structures after the occurrence of an earthquake. This EDP is used as an index to decide about the retrofit or demolition of structures. The main purpose of this study is to evaluate the effects of using linear and nonlinear Fluid Viscous Dampers (FVDs) on the MRIDR response of steel Special Moment Resisting Frames (SMRFs) with FVDs. Moreover, two vertical distributions of damping coefficients including Uniform Distribution (UD) and Interstory Drift Proportional Distribution determined based on the first mode deformations (IDPD) are compared for the structures considered. The values of median MRIDR capacity, median SaRD, corresponding to different MRIDR levels are determined by performing Incremental Dynamic analyses (IDAs). After computing the median SaRD for a specified MRIDR level and its corresponding logarithmic standard deviation, the Mean Annual Frequency (MAF) of exceeding that MRIDR level (λRD) is computed. Based on the results, the values of median SaRD for structures with linear FVDs are higher than those for structures with nonlinear FVDs, and hence the values of λRD corresponding to structures with linear FVDs are lower than those for structures with nonlinear FVDs. In addition, for structures with a soft story, using IDPD to determine damping coefficients results in higher median SaRD values, and hence lower λRD values.