Parameters affecting the fundamental period of RC buildings with infill walls

In this study, the effects of selected parameters i.e. building height, number of bays ratio of area of, shear walls to area of floor, ratio of infilled panels to total number of panels and type of frame on the fundamental period of RC buildings were investigated. In general, the fundamental period of RC frames are determined by a modal analysis, by discarding the effect of infill walls on the total mass and rigidity of the structure. 189 building models with selected parameters were generated and analyzed in 3D using a finite element method. Due to the nonlinear behavior of infill walls, an iterative modal analysis was used to determine the fundamental period of models. It was found that RC frames with infill walls had a shorter period. about 5%-10%, compared with RC frames without infill walls regardless of whether they had shear walls or not. The presence of shear walls also led to a reduction in the fundamental period, about 6%-10%, between models with and without infill walls. The fundamental periods obtained by an iterative modal analysis were also compared with current code predictions, which are based on measurements taken during earthquakes on real buildings. It was seen that the current code equations under-predict the fundamental periods of the models from 2% to 47%, depending upon the model parameters. A new equation, which was a function of the selected parameters, was also proposed for predicting the fundamental period of buildings. based on results of this study using multiple linear regression analysis. The proposed equation gives a better estimate of fundamental periods, compared with the code equations. (C) 2008 Elsevier Ltd. All rights reserved.