Effect of seismic sequences on behavior of mid-rise steel moment-resisting frames equipped with fluid viscous dampers

This study aims to investigate the seismic response of mid-rise steel frames equipped with fluid viscous dampers under seismic sequences. For this purpose, 4-, 6-, and 8-story steel frames with and without fluid viscous dampers are analyzed under sequences of main shock and after shock, both with near and far field acceleration records. Thus, sets of 20 near-field and 20 far-field time histories are selected, each containing the main-shock and an after-shock. Using nonlinear dynamic analysis, the responses of the frames are calculated and plotted in various diagrams. Output parameters of displacement, interstory drifts, base shear, absolute acceleration and velocity are extracted and compared. Results show that viscous dampers significantly decrease structural responses comparing to the frames without damper. Also, structural responses have increased under combination of main -shock and after-shock which shows the important role of after-shocks in structural damages. Responses to near field record are also generally greater than far field ones.