Hindawi Publishing Corporation Advances in Civil Engineering Volume 2013, Article ID 517454, 12 pages http://dx.doi.org/10.1155/2013/517454 Research Article Seismic Vulnerability Assessment of a Historical Church: Limit Analysis and Nonlinear Finite Element Analysis G. Castellazzi, C. Gentilini, and L. Nobile Department of Civil, Chemical, Environmental, and Materials Engineering, University of Bologna, v.le Risorgimento 2, 40136 Bologna, Italy Correspondence should be addressed to G. Castellazzi; giovanni.castellazzi@unibo.it Received 6 May 2013; Accepted 25 June 2013 Academic Editor: John Mander Copyright © 2013 G. Castellazzi et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te seismic vulnerability of a historical Basilica church located in Italy is studied by means of limit analysis and nonlinear fnite element (FE) analysis. Attention is posed to the failure mechanisms involving the fac ¸ade of the church and its interaction with the lateral walls. In particular, the limit analysis and the nonlinear FE analysis provide an estimate of the load collapse multiplier of the failure mechanisms. Results obtained from both approaches are in agreement and can support the selection of possible retroftting measures to decrease the vulnerability of the church under seismic loads. 1. Introduction Recent Italian seismic events, such as the Emilia (2012) and the L’Aquila earthquakes (2009), have demonstrated how churches are susceptible to damage when subjected to earth- quake motions [1–3]. In fact, designed to withstand vertical loads, churches in general present slender walls, lack of hor- izontal structures, weak or nonexistent connections among structural elements, absence of efective tie-rods to absorb arch thrusts [4], and irregular stone texture. Tese aspects, added to poor material performance especially in tensile stress mode [5], are among the reasons for the structural collapses of historical monumental buildings when subjected to seismic forces. Cases of damaged or collapsed churches afer earthquake events (sometimes also immediately afer their renovations) are numerous. It is worthwhile to remember the collapse of St. Possidonio church (Italy) in 2012, the partial collapse of the church of Santiago in Lorca (Spain) in 2011, the collapse of the Catholic Cathedral of Port au Prince in Haiti in 2010 (right afer its total restoration), and the partial collapse of the main church in St. Pietro di Coppito (Italy) in 2009, afer consistent work of conservation. In the literature, the approaches employed to analyze the seismic behaviour of masonry structures can be sum- marized as follows: micromodeling approaches (see e.g., [6, 7]), macromodeling approaches (see e.g., [8]), multiscale approaches (see e.g., [9]), and full-scale approaches (see e.g., [10–14]). Among these methods, the most suitable to determine the seismic vulnerability of masonry buildings are the latters that correspond to limit analysis and nonlinear FE analysis [15, 16]. Both approaches aim at providing the value of the load that activates the failure mechanisms of the macroelements in which the church can be subdivided. In fact, the behavior at collapse of a masonry church under a seismic event is rarely global since several out-of-plane collapses of macroelements may occur. Te experience suggests to consider a limited number of possible failure mechanisms involving the main elements of the church such as the fac ¸ade, the apse, the naves, the triumphal arch, and the navy walls. Within this context, the present study presents a nonline- ar FE analysis coupled with a limit analysis applied to Madre Santa Maria del Borgo, an Italian church located in San Nicandro Garganico. In particular, the collapse mechanisms involving the fac ¸ade are analyzed in detail, since reputed potentially critical afer a survey. Tree mechanisms are iden- tifed: an out-of-plane mechanism of the fac ¸ade, a mechanism involving the fac ¸ade and the peripheral lateral walls, and a mechanism considering the interaction between the fac ¸ade, the peripheral lateral walls, and the navy walls.