Seismic collapse analysis of high-rise reinforced concrete frames under long-period ground motions

Structural damages associated with buckling of longitudinal reinforcing steel and crushing of concrete induce strength and stiffness degradation in reinforced concrete (RC) beams and columns. This paper presents a numerical investigation on earthquake-induced damages and collapse of typical high-rise RC buildings model incorporating strength degradation (SD) effects. In a simple finite-element analysis program with the generalized stress fiber discretization, hysteretic constitutive models primarily dominate the inelastic behavior. Buckling of reinforcing steel and crushing of confined concrete are taken into accounted to the stress-strain relationship of fiber elements. The SD effect in components with small hoop ratio tends to amplify the seismic responses high-rise RC moment-resisting frames when the intensity of ground motions exceeds the design level. Buckling of steel rebar and crushing of concrete should be fully considered together with the P-Delta effect for collapse simulations.