Hybrid Force-Displacement based Seismic Design Method for Eccentrically Braced Steel Frames

In this research, the performance-based seismic design method for eccentrically braced frames has been implemented which combines the advantages of the force based and displacement based design methods “so called” hybrid force-displacement design method (HFD). This method is started by transforming of maximum inter story drift and local ductility into target roof displacement and then for ductility and strength reduction factor, proposes some relations. In this research, hybrid method for eccentrically braced steel frames has been applied. For this purpose, sixty eccentrically braced steel frames with different number of stories, bay widths, number of spans, various bracing dimensions, etc.. have been analyzed using nonlinear static analysis method (Push Over Analysis). Then, the nonlinear multiple-parameter regression model has been utilized for proposing the formulas for strength reduction factor and ductility. Obtained relations are influenced by lateral loading system type, earthquake level, slenderness of braces, intensity of earthquake, number of roofs and bays. The obtained results in compare with force based and direct displacement based methods show the reliable accuracy in roof displacement and base shear that lead to economical design of structures.