RESPONSE OF MASONRY STRUCTURES SUBJECTED TO LATERAL LOADING

Abstract

Masonry is one of the oldest building materials known to mankind. Unreinforced masonry has been popular owing to its numerous advantages. However most of the unreinforced masonry constructions are non-engineered and hence vulnerable to seismic forces. There has been large scale loss of life and property due to collapse of these structures during past earthquakes. Also, with ever increasing clamor for green construction and environment conservation, retrofitting such structures rather than demolishing is currently attaining major attention. A typical unreinforced masonry building was chosen and its seismic retrofit was performed. Pier analysis method was used to evaluate the safety of the structure under combined gravity and earthquake forces. Tension failure was observed in in-plane and out-of-plane action of walls and hence the structure was suitably retrofitted by providing splints and bandages with galvanized wire mesh. Further, the seismic evaluation of an old unreinforced masonry building in New Delhi was performed. Pier analysis results indicated that large number of piers was failing in in-plane tension, in-plane shear and in out-of-plane tension. Feasibility of retrofit of the structure was also studied. Behavior of masonry structures during earthquake is a complex phenomenon. Better understanding of the dynamic response of these structures can be achieved using finite element studies. SAP2000 v17 software was used to model the above considered typical unreinforced masonry building. It was also intended to model the structure with the retrofit scheme suggested as per the manual procedure and study its feasibility. But, after exploring the software, it was understood that an orthotropic nonlinear analysis could not be performed. Also, due to lack of orthotropic properties of masonry, an isotropic linear dynamic analysis was performed on the model without retrofit and the finite element and pier analysis results were compared. Large difference was observed in the tensile stresses due to out-of-plane bending while stresses in the in-plane action were comparable.