Considering the nonlinear behavior of R.C.C., parametric studies are performed in this thesis to investigate some important details of the dynamic behavior of R.C.C. structures. Simple three-dimensional frames are taken for nonlinear dynamic analysis under combined vertical load and seismic vibrations on the short direction of a number of buildings (2, 5 and 10 storied). In this study the ground motion data from two earthquakes; i.e. El Centro earthquake, USA (1940) and Kobe earthquake, Japan (1995) are used.

Three-dimensional nonlinear dynamic analyses are conducted on 2, 5 and 10 storied buildings with adequate structural dimensions. The maximum shear forces often occur in the critical central beam and columns of these buildings, which are taken for illustration of the results. Described in this study are the differences in the shear forces and deflections obtained from 2D nonlinear, 3D nonlinear and 3D linear analysis. The failure criteria and permanent deformations of the structural members are two of the most important characteristics studied in the nonlinear analyses.