Nonlinear analysis of out-of-plane masonry façades: full dynamic versus pushover methods by rigid body and spring model Siro Casolo 1, * ,† and Giuseppina Uva 2 1 Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, Italy, I-20133 2 Dipartimento di Scienze dell’Ingegneria Civile e Architettura, Politecnico di Bari, Via Orabona 4, Bari, Italy, I-70125 SUMMARY The paper proposes a systematic comparison between two methods of analysis that are well established in the field of earthquake engineering: nonlinear dynamic analysis and nonlinear static procedure (NSP), applied to the out-of-plane seismic response of two masonry façades representative of many ancient Italian churches. The comparison is based on extensive numerical analyses, which focus on the flexural and torsional mechanisms, while the in-plane damage mechanisms and the possible detachment between the façade and the lateral walls because of a poor connection have been presently disregarded. The computa- tions, both in the static and in the dynamic field, are based on a rigid body and spring model specifically implemented for this issue, computationally efficient and equipped with a realistic model of damage and hysteresis at the mesoscale. An innovative aspect of this study is the heuristic modelling of three-wythe masonry, to include some typical texture effects on the macroscale nonlinear response. For each façade, two different masonry textures were considered, performing extensive dynamic analyses that offered a detailed overview about the performance under earthquakes of different intensities. In parallel, NSP and the classical N2-based seismic assessment were applied. A critical discussion and comparison of the results of the two methods is presented to rationally appraise limits and opportunities. In particular, flexural and twisting out-of-plane mechanisms were clearly appraised in the dynamic field, whereas NSPs were not always able to describe the collapse, because they missed the partial failures determined by higher vibration modes, as could be expected. Copyright © 2012 John Wiley & Sons, Ltd. Received 31 December 2011; Revised 1 April 2012; Accepted 17 May 2012 KEY WORDS: dynamics; pushover; seismic assessment; masonry; out-of-plane; RBSM; damage mechanism 1. INTRODUCTION The seismic assessment of historical masonry buildings is still an open challenge for the researchers operating in the field of structural engineering devoted to the protection of cultural and architectural heritage. Historical buildings are in fact characterized by a peculiar response, and the seismic assessment requires specific models and procedures [1], which are not yet well-established and validated. Within this framework, the research paper is focused on the development and application of a computational approach oriented at the solution of the elasto-plastic problem for realistic structures at the macroscale in a complex operational context. The present research is specifically devoted to the out-of-plane response of the façade of historical masonry churches, which are widespread on the Italian territory and all around the Mediterranean Sea, in earthquake prone areas. Historical masonry churches represent a particularly vulnerable architectural class, because of their peculiar morpho-typological characters. The after-earthquakes surveys and a large number of related *Correspondence to: Siro Casolo, Dipartimento Ingegneria Strutturale, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, Italy, I-20133. † E-mail: Siro.Casolo@polimi.it Copyright © 2012 John Wiley & Sons, Ltd. EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS Earthquake Engng Struct. Dyn. (2012) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/eqe.2224