EMPIRICAL EVALUATION OF DUCTILITY FACTORS FOR THE SPECIAL STEEL MOMENT-RESISTING FRAMES IN VIEW OF SOIL CONDITION

摘要

It is well known that the response modification factor (R) takes into account the ductility, over-strength, redundancy and damping of structural systems. The ductility factor has played an important role in seismic design, as it is a key component of R. In this study, the ductility factors (R_(μ,MDOF)) of special steel moment-resisting frames are calculated by multiplying the ductility factor of single degree of freedom (SDOF) systems (R_(μ,MDOF)) with the multi-degree of freedom (MDOF) modification factors (R_M). The ductility factors (R_(μ,MDOF)) of SDOF systems are computed from non-linear dynamic analysis undergoing different levels of displacement ductility demands and periods when subjected to a large number of recorded earthquake ground motions. To compute the R_(μ,MDOF)). a group of 1,860 ground motions recorded from 47 earthquakes were considered. R_M factors are proposed to account for the MDOF systems, based on previous studies. A total of 108 prototype steel frames were designed to investigate the ductility factors, considering design parameters such as the number of stories (4, 8 and 16), framing systems (perimeter frames and distributed frames), failure mechanisms (strong column-weak beam and weak column-strong beam), soil profiles (S_A, S_C and S_E in Uniform Building Code 1997) and seismic zone factors (Z = 0.075, 0-2, and 0-4 in UBC 1997). The effects of these design parameters on the R_(μ,MDOF)of special steel-moment-resisting frames were investigated.