TORSIONAL RESPONSE OF UNREINFORCED MASONRY BUILDINGS: NONLINEAR TIME-HISTORY AND PUSHOVER ANALYSES

The paper deals with the inelastic torsional behavior of unreinforced low-rise masonry buildings. The buildings are studied through the finite element method, adopting a damaged plasticity model. First, the nonlinear time history response of asymmetric-plan buildings under different seismic inputs is compared with one of the counterpart symmetric variants to assess the magnitude of torsional coupling. Increases in displacement at the flexible side similar to that usually measured in torsionally stiff frame buildings are computed, whereas all the walls undergo comparable damage. The response history of floor displacement and base shear allows investigating the evolution of the damage in the walls during the time history. Subsequently, the suitability of 3D pushover analysis, performed under two invariant distributions of lateral forces, is assessed comparing the horizontal displacements and damage at walls with the ones provided by nonlinear time-history analyses. It is shown that pushover can adequately evaluate floor displacements but significantly underestimates damage at walls, especially at the inner walls, which undergo the same damage to the perimeter walls but less displacement.