Energy-based Seismic Design Method Of Self-centering Concentrically Braced Steel Frame Structures Under Near-fault Earthquake

Due to the obvious high energy velocity pulse characteristics of earthquake wave recorded in near-fault region,the building will produce the significantly large residual deformation,which increases the repair difficulty and cost after earthquake.Some buildings have to demolish without economical rehabilitation.The current Chinese seismic code adopts the elastic method for designing building under small earthquake,and expects the buildings enter into the elastic-plastic state and produce the desirable failure mode.So,the energy-based seismic design method for structures located in near-fault earthquake regions has been paid much attentions by many researchers.Based on the previous research results and energy balance criteria,this paper introduces the Maximum Effective Cyclic Energy(MECE)Spectrum to consider the instantaneous input energy of near-fault ground motion,and establishes the simplified calculation formula of the MECE for SC-CBSF structure.Finally,the energy-based seismic design method for self-centering concentrically braced steel frame(SC-CBSF)structures considering the near-fault earthquake characteristics was proposed,and the rationality of this innovative design approach was evaluated by using nonlinear time-history analysis.The main research contents of this paper are as follows:(1)The shear force distribution mode and the desirable yielding mechanism of the SC-CBSF structure at elastic-plastic state were illustrated,and the energy calculation expressions of the main components of SC-CBSF structure were presented.According to the MECE spectrum and energy balance principle,the seismic design method based on MECE spectrum for SC-CBSF structure located in near-fault earthquake regions was proposed.(2)Considering the influence of the target ductility and storey number,four SC-CBSF examples with five storeys(?_t=2,4)and ten storeys(?_t=2,4)were designed according to the proposed seismic design approach.The hysteretic behavior and self-certering behavior of SC-CBSF examples was carried out and evaluated.(3)A total of 40 near-field earthquake waves with velocity pulse effect were used to perform the nonlinear time-history analysis upon these four SC-CBSF examples at rare earthquake level.The story shear force distribution,story displacement,residual story displacement,inter-story drift ratio angle and residual inter-story drift ratio angle were evaluated.The reliability of seismic design method for SC-CBSF structure based on the MECE spectrum was confirmed.(4)Additionally,the capacity spectrum method was also adopted to evaluate the seismic behavior of four SC-CBSF examples,and the reliability based on the MECE spectrum design was re-confirmed.