بررسي مقاومت افزون و شاخص قابليت اطمينا ن در قابهاي فولادي با ديوارهاي ميانقاب بنايي

Previous experience earthquakes and experimental evidences have presented that structures display extra strength than which have been designed under lateral loads. This is due to the presence of the remarkable stored strength which is not considered in the design. This strength is called over-strength which is defined by over-strength factor. This factor depends on different elements, such as redundancy degree, ductility, type of the lateral force resisting system and intensity of the seismic hazard zone. Infill walls are used in the most buildings based on architectural reasons. Presence of infill walls cause to change in stiffness, strength, ductility and consequently can cause change in over-strength factor. The aim of this study is to evaluate the effect of infill walls on the over-strength and reliability index. Therefore some steel frames with various stories and bays were considered. The studied frames were evaluated on the basis of nonlinear analysis (pushover) in two cases of with and without infill walls by ETABS software and the results is figured in the displacement-base shear curves. It is found that presence of infill walls caused increase in strength and decrease in structural ductility.