Assessment of current nonlinear static procedures on the estimation of torsional effects in low-rise frame buildings

The capability of current nonlinear static procedures in capturing torsional effects was evaluated by comparing their estimates to the “exact” results, obtained from nonlinear response history analyses under a ground motion ensemble scaled to 3 different hazard levels. Two different types of eccentricities were considered. In the first case, the mass center of the floor of a symmetric plan structure was shifted in one direction to create a uni-directional eccentricity and in the other case a structure with a plan asymmetry in both horizontal directions was used. Results of numerical analyses show that far-fault and near-fault ground motions have similar influences on the displacement demand of structures as far as torsional effects are concerned. The recent nonlinear static procedures proposed for asymmetric buildings were found to be effective in capturing torsional effects whereas the classical nonlinear static procedure developed originally for planar systems significantly underestimates torsional rotation demands in structures.