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INVESTIGAnON OF NONLINEAR BEHAVIOR OF BENDING R.C. FRAMES STRENGTHENED BY STEEL BRACINGS

In this paper, the nonlinear behavior of R.C frames strengthened by shear walls and steel bracings is investigated. The use of steel bracing and R.C shear wall for strengthening of existing R.C structures usually leads to very complicated system and the study of the behavior of this kind of structures especially their connections, steel bracing area, and frame - shear walls and bracing interaction is necessary. In this study, a ten - story R.C. structure is analyzed using a nonlinear finite element program in four stages. In first stage; R.C frame, in second stage; frame with shear walls, in third stage; frame with shear wall and bracing and in fourth stage; frame with bracings is studied. The analytical results show that the application of shear walls causes an increase in strength and stiffness of structure but a decrease in ductility. Compared with shear walls, bracings have less effect on the strength of system but increase the ductility. The modulus of elasticity in strain - hardening part of stress - strain curve of steel has significant effect on the behavior of structure and leads to some numerical problems.