Analysis of Aseismic Behavior of Multistory Frames Based on Different Braces Design Methods

The current criterion of braces design with amplifying the earthquake force may lead to columns′ buckling,a design method of weak-shear braces is suggested.The nonlinear elastic-plastic time-history responses of these braced frames under earthquake records are analyzed by FEA.It was found that the columns in strong-shear braced frames will buckle in a non-sway mode before yielding,and then the horizontal displacement of the frame increases rapidly.But the deformation of a weak-shear braced frame is in a sway mode.Curves of inter-story shear force-lateral displacement and the stress-strain response of the brace and the column do not form a hysteretic loop in the strong-shear frame,and the energy dissipating capacity is unable to reduce the earthquake response.In the weak shear frame,the brace yields earlier than the column,therefore the brace and the frame may deform laterally continuously to develop their ductility and the energy-dissipating capacity to reduce the earthquake response.It is suggested that check must be carried out to make sure that the brace yields before the column buckle in a non-sway mode.