Strength Reduction Factor And Structure Influencing Factor Of One-story Steel Frames

Generally, the structures will enter the inelastic range in event of severe ground motion, and many factors many influence the inelastic response of structures. In order to implify the method, the concept of modifiction factor of earthquake action is introduced in the seismic codes over the world, but factors in these codes are differents. Factors are related with structure system, ductility level, overstrength in the codes abroad. In Chinese code the diferences between structure system, period of time and earthquake hazard areas of structure are not taken into accout, and the uniform numeric value is used for the reduction factor. Therefore, some questions may be asked about it. Many scholars in China appeal for revision of structure influencing factor. The contents of this paper include several aspects as follows:(1) By the nonlinear time-history analysis, the ductility reduction factor spectra of SDOF system are proposed.According to the design characteristic period in Code for Seismic Design of Building (GB50011-2001), the fitting expressions of the strength reduction factors for design are given.(2) The effects of fortification intensity, site conditions, earthquake magnitude, epicentral distance for earthquake event and natural vibration period, ductility, damping ratio,post rigidity on strength-reduction factor for structures are investigated. In addition, the modified expressions of modifying the strength reduction factors are presented.(3) According to Chinese seismic code, two models of one-story steel frames are designed.By finite element analysis software ,static nappe and time-history dynamic analysis are performed to get structure modification factor of earthquake action(R) and structure influence factor(C) of one-story steel frames.