Nonlinear dynamic numerical analysis of a RC frame subjected to seismic loading

Abstract

In the context of seismic engineering, reliable modeling methodologies are needed to represent the nonlinear dynamic behavior of structures under the effect of the seismic action. Only in this way is it possible to assess the safety margin against structural collapse. However, in the case of reinforced concrete (RC) structures, numerical modeling still presents difficulties due to complex nonlinear material behavior. The aim of this paper is to evaluate the capability of numerical modeling with solid finite elements to represent a strongly nonlinear dynamic response of reinforced concrete structures under the effect of the seismic action. A second objective is to obtain modeling guidelines for this dynamic behavior. A numerical study was performed in order to reproduce the nonlinear dynamic response of a RC frame tested by Elwood and Moehle (2003) on a shaking table at the University of California, Berkeley (USA). A material model that employs the shear failure surface proposed by Ottosen (1977) was selected to represent the non-linear behavior of concrete. This material model has several parameters that define their behavior, which includes the crack width at which tensile stress decreases to zero after a strain softening process. This parameter and the strain based erosion limit were subjected to calibration. During the calibration process, the degree of numerical-experimental similarity was established along with conclusions about the sensitivity of numerical response to variations of the calibrated parameters. Finally, it can be concluded that the numerical model reproduces the nonlinear response with sufficient accuracy. Moreover, the explicit time integration scheme shown to be appropriate for this type of problem with strong nonlinearities and degradation of the concrete.