The Earthquake Engineering Online Archive

Modal pushover analysis for seismic evaluation of reinforced concrete special moment resisting frame buildings

Bobadilla, Hugo; Chopra, Anil K.

UCB/EERC-2007/01, Earthquake Engineering Research Center, University of California, Berkeley, 2007-10-03, PDF (1.07 MB)

Now standard in structural engineering practice worldwide is the nonlinear static procedure known as pushover analysis described in FEMA-356 and ATC-40 guidelines for seismic evaluation of existing buildings. Several researchers have suggested that in this procedure seismic demands (story drifts and plastic rotations) are underestimated in the upper stories of buildings where higher-"mode" contributions to response can be significant. To address these limitations, improved nonlinear static procedures have been developed, one of these being the modal pushover analysis (MPA). The median seismic demands for 4-, 8-, 12-, and 20-story reinforced concrete special moment resisting frame (RC-SMRF) buildings--designed according to current building codes and subjected to an ensemble of 78 ground motions--were computed by MPA and nonlinear response history analysis (RHA) procedures and compared. For the most intense excitations, which represent a very severe test, the MPA procedure estimates seismic demands for RC-SMRF buildings to a useful degree of accuracy; in contrast the FEMA-356 force distributions are inadequate in estimating seismic demands for 8-, 12-, and 20-story buildings at all intensities, from the weakest that causes response essentially within the linearly elastic range, to the strongest that drives the buildings far into the inelastic range.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-07-01.pdf (1 MB)