The Seismic Response Modification Factors Of Eccentrically Braced Chevron Steel Frames

Building structure can enter elastic-plasticity to consume the earthquake energy and diminish the earthquake effect in strong motion earthquake, the bottom shear elastic response to be significantly less than at the bottom of the shear.Without regarding the type of structure and material, the code for Seismic Design of Building (GB50011-2001) take the same value (2.8125) of seismic modification factors R in different structural systems. So the good capacity of energy-disspation and ductiliy of steel structure cannot be used surfficiently according to the code. After carefully studying the papers about the seismic modification factors, the method based on incremental dynamic analysis are presented for the seismic modification factors.In this paper, nine Eccentrically braced chevron steel frames (including 11-story, 18-story, 25-story,3-span,5-span, 6.6 meter span and 9 meter span) are designed and analyzed with selected seismic record by incremental dynamic analysis method. And their seismic modification factors are investigated. On the basis of the results, tentative seismic modification factors are proposed for eccentrically braced chevron steel frames dual systems.The paper studies the relationship between the seismic modification factors and other factors such as the number of storeys, spans , span numbers,and the cycle of frames. Finally, the discipline of storeys, spans , span numbers ,cycle of frames on the behaviour factors are given.