Siro Casolo Politecnico di Milano, Dipartimento di Ingegneria Strutturale, Italy ABSTRACT: The paper presents a specific computational model for the in-plane dy- namical analysis of masonry walls subjected to earthquakes. The model formulation is based on two main considerations: i) the building performance is related to the energy dissipation capacity of the material; ii) the damage mechanisms are influenced by the masonry texture. Clearly, non-linear dynamics requires models with few degrees of free- dom together with the assumption of simplified hypotheses about the material response. As a consequence, it is essential to balance the needs of an adequate description of the building geometry with a realistic post-elastic material modelling. To do this, the pro- posed method adopts rigid elements connected by line springs that are defined in order to obtain a phenomenological description of the cyclic response and degradation of the masonry material. The proposed mechanistic formulation is presented in the frame of a global seismic analysis of a real masonry monument. 1 INTRODUCTION The seismic analysis of monumental masonry buildings is the main interest of the present research. These structures have specific architectonic parts, such as large fa¸cades, pillars, slender columns, arches and vaults that often suffer damage and mechanical degradation even when subjected to moderate earthquakes. In this case, in order to obtain a reliable estimation of the seismic risk, it is desirable to perform full dynamical analyses that de- scribe the effective transmission and dissipation of the energy coming from the ground motion into the structure (Bertero, 2002; Housner, 1970; Petrini and Casolo, 2002; Uang and Bertero, 1990). At present, modelling the non-linear mechanical behaviour of masonry monuments by means of three-dimensional models require a great amount of computational resources that are not commonly available. Luckily, it is often effective to subdivide these monuments into “macro-elements” (e.g. the fa¸cade, the lateral walls, the triumphal arch, the bell tower, the apse), since the seismic response of these single parts tends to be dominated by recurrent damage mechanisms, and the mechanical interrelation between contiguous parts is limited (Doglioni et al., 1994; Petrini et al., 1999). In particular, when performing complete dynamical analyses it is often preferable to adopt a two-dimensional model rather than a three-dimensional (Louren¸co, 2002), even if the definition of a simpler model often requires a process of tuning in order to approximate as well as possible the features of the specific kinematics that is of interest. In the present paper this strategy is applied to the seismic analysis of the large medieval Structural Analysis of Historical Constructions, New Delhi 2006 P.B. Lourenço, P. Roca, C. Modena, S. Agrawal (Eds.) A Specific Rigid Element Model for Macro-Scale Dynamics of Monumental Masonry considering Damage and Micro-Structure Effects