Seismic behavior of the weak-shear braced frame

There may exist deficiencies in current codes for strong-shear braced frame designed by amplifying design force of braces artificially.The weakshear brace design was thereby developed to solve the problem.The nonlinear elastic-plastic time-history responses of the two types of frames under 10 earthquake records were analyzed by using finite element analysis(FEA) method.Results show that columns in strong-shear braced frames will buckle in a non-sway mode before yielding of the braces,and then horizontal and vertical displacement of frame increases rapidly.But the deformation of 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 energy dissipating capacity is unable to be developed 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 should be carried out to insure that the brace yields before the column buckle in a non-sway mode,which make the structure to be a strong column weak brace system.