Performance Based Seismic Evaluation of RC Frames with Floating Columns

Shah B. A. Associate Professor, Applied Mechanics Department, M. S. University of Baroda, and Patodi S. C. Professor, Civil Engg. Department, Parul Institute of Engg. & Tech., Limda, Baroda.

In the present study, a mathematical model of a G+7 storey space frame having nine columns at all the panel points of a 3m x 3m grid with an overall plan dimension of 6m x 6m is considered. The effect of omitting a column from the first storey to sixth storey on seismic performance of an RC space frame is studied. Rectangular and equivalent square cross sections of columns are considered for comparison under push over analysis using commercially available ETABS software. Base shear, roof displacement, effective time period and effective damping are reported at performance point for all the models developed. The storey drift plots are also compared for square and rectangular column frames having a transfer girder carrying columns up to six floors above it. It is observed that for the frames with transfer girders carrying less than three floors above it do not have a significant effect on the seismic performance. Also, the square shaped columns are found to perform better than the rectangular columns under similar situation of floating columns.