UNSYMMETRIC-PLAN MASONRY BUILDINGS: PUSHOVER VS NONLINEAR DYNAMIC ANALYSIS G. Faella 1 , A. Giordano 2 and M. Guadagnuolo 3 ABSTRACT This paper deals with the inelastic torsional behavior of unreinforced low-rise masonry buildings. First, the nonlinear dynamic response of unsymmetric-plan buildings under different seismic inputs is compared with the one of the counterpart symmetric variant in order to assess the torsional coupling arising from unsymmetry. The buildings are studied through the finite element method, adopting suitable constitutive models which implement well known concepts of damaged elasticity in combination with tensile and compressive plasticity. The accuracy of 3D pushover analysis, performed with two invariant distributions of lateral forces, is then assessed comparing the results in terms of horizontal displacement and damage at walls with the ones provided by the nonlinear time- history analysis. It is shown that pushover can adequately evaluate floor displacements but significantly underestimates damage at walls, even if combined with results of linear dynamic spectral analysis. Introduction The observation of earthquake damage indisputably showed that besides the quality of masonry material, building configuration is of remarkable importance. Masonry buildings with regular structural layout and walls well connected together at floor levels frequently showed satisfying performance, even when not designed to resist earthquakes. In fact, if the building structure is regular, gravity and seismic loads are evenly distributed among resisting elements, seismic energy can be dissipated almost uniformly over the entire structure. Symmetric-plan distribution of resisting elements can prevent significant torsional vibration that frequently causes unexpected response when the building structure is subjected to strong input ground motion. Although the traditional masonry structural systems consist of load-bearing walls and cross walls that have simple plan distribution and constant thickness along the height, masonry buildings often show torsional response under earthquake. Many buildings are indeed not approximately symmetrical along each principal axis in plan, regarding both lateral stiffness and mass distribution, also because windows are of different dimensions and not aligned. The plan configuration recurrently results from composite shape (L, T, U, etc.), whereas long rectangular 1 Professor, Dipartimento di Cultura del Progetto, Second University of Naples, Aversa, Italy 2 Ph.D., Dipartimento di Ingegneria Strutturale, University of Naples Federico II, Naples, Italy 3 Ph.D., Dipartimento di Cultura del Progetto, Second University of Naples, Aversa, Italy Proceedings of the 9th U.S. National and 10th Canadian Conference on Earthquake Engineering Compte Rendu de la 9ième Conférence Nationale Américaine et 10ième Conférence Canadienne de Génie Parasismique July 25-29, 2010, Toronto, Ontario, Canada • Paper No 863