Use of pushover analysis for plan irregular buildings

It is well known that in order to use pushover analysis for predicting seismic response of plan irregular structures, as an alternative to the nonlinear dynamic analysis, special procedures need to be used, since effects of torsional response become important. A method recently proposed by Fajfar et al. (2005), which constitutes an extension of the well-known N2 method, appears very promising and it is used in this paper to check the ability of pushover analysis to predict response of plan irregular structures. The ability of pushover analysis to predict non linear seismic behavior through the modification proposed by Fajfar et al. (2005) is checked for a L-shaped plan types configuration. Namely, a five storey framed reinforced concrete building presenting such plan configuration and designed according to current code procedures is analyzed by means of non linear dynamic analysis and the obtained results are compared to those from modified pushover analysis. An ensemble of seven earthquake records, carefully selected in order to represent the Italian code seismic action (very similar to the Eurocode 8 one), is used as input ground motion for the nonlinear dynamic analysis. Both top storey and interstory drifts are considered as response parameters in order to carry out a more reliable comparison.