Composite Steel plate shear walls (C.S.S.W.) have been used in structures as a lateral resisting system that it’s building by concrete cover on one or both sides of steel plate. This system that identifed as the 3rd version of the shear walls, by increasing of stiffness, ductility & energy absorption is widely used in tall building, retrofitting of structures and tanks.
In this paper, evaluation of concrete layer to steel plate thickness ratio has been investigated on C.S.S.W. behavior. In this regard, some experimental and analytical specimens involved of flexible steel fram, steel shear wall & steel plate shear wall composited with reinforced concret layer are built and tested using a rigid frame and actuator. The variable parameters on composite shear wall were the number of concrete layer, distanse between stuts and ratio of steel plate to of concrete layer thickness. The results show that the stiffness of composite shear wall has direct proportion to concrete layer thickness and has inverse proportion to distance between stuts. Increasing on proportion of thickness of steel plate to thickness of concrete layer until optimum thickness reduced the displacement of out of plate and beyond which there would be no merit. On the other hand, usage of two concrete layers on two side of steel plate was reduced effect of secandary bending.