Seismic damage evaluation of unreinforced masonry buildings in high seismic zone using the nonlinear static method

Abstract

Seismotectonic features of northeast India signify a very high probabilit of occurrence of major earthquake in future. However, a considerable portion of the building stock of this region is unreinforced masonry buildings. These buildings possess very little displacement capacity and consequently a devastating effect maybe observed during a future earthquake. Therefore, potential seismic evaluation of unreinforced masonry buildings in these areas is very essential in order to implement any kind of seismic hazard mitigation strategy. In this study, seismic evaluation of representative masonry building models is carried out by performing pushover analysis using available computer program SAP2000. In this method the masonry walls are modeled as equivalent frame made of vertical (pier) and horizontal (spandrels) elements with rigid intersecting joint elements and lumped plastic hinge concept. The model simulates nonlinear in-plane behaviour of the wall panels. The shear failure of spandrel is addressed by shear hinge at the middle and acombined failure of pier is addressed by two P-M interaction hinges at either end of the pier. However, combined failure is governed by the minimum failure envelopeof P-M interaction curves to ensure the effect of vertical load on the failure of pier. Lastly, fragility curves which express the expected damage as a function of spectraldisplacement were developed based on the capacity curve.