The present study deals with dynamic nonlinear analyses of reinforced concrete columns in order to examine the failure modes and maximum displacement response.In the paper, first, the three kinds of failure modes are defined: shear failure, shear failure after the yielding of main reinforcement, and bending failure.In particular, the shear strength degradation in the truss analogy is modeled by introducing the reduction formula given by Priestley, et al.
The various numerical simulations of single type of columns are carried out under the two types of the recorded strong ground motions.The degradation process of shear strength of concrete are realistically observed during the random time-history response.The reduced shear strength is compared to the design values specified in the Japan's seismic design codes.