Numerical Modelling of Masonry Buildings: benchmarking of finite element approaches

Nonlinear analysis to support structural design in seismic zone is becoming a current topic in professional activities due to first the OPCM 3274/2003 and the 3431/2005 and finally the NTC 2008. These methods, even known as pushover analysis are needed in particular when dealing with masonry constructions. Several software houses provide numerous tools to support the professionals in their consultancy activities. Despite the number of models available, often the results are affected by uncertainty. Different software normally start from different mechanical models and this leads to results affected from numerical approximation not well known to the users.

Even more, experimental results with regard to masonry buildings are few and this makes difficult calibration of the numerical model.

 In this paper an innovative approach is presented based on a macro modelling formulation of the masonry panel. A new finite element (FE) has been implemented in the CDS (Computer Design of Structures)-OpenSees (Open System for Earthquake Engineering Simulation) software within the framework of a wider collaboration aiming at promoting in the professional world the use of accurate and effective FE  by endowing them with user-friendly graphical interfaces.

To benchmark the new approach, well known experimental results available in the literature are used. They are obtained from tests on scaled prototypes of masonry buildings. At the same time commercial software widely spread in the practise are used to analyze the same case studies (MIDAS Gen distributed from CSPFEA and 3Muri distributed from S.T.A. DATA). Each software starts from a different formulation of the constitutive law  and of the meshing strategies (homogenized formulation, micro and macro modelling of the masonry block and interfaces, 1D, 2D and 3D mesh). The comparison of the results allows to identify advantages and drawbacks of each numerical approach.