Numerical model for the cyclic behaviour of a rubble stone masonry wall with opening and reinforcement

Historical buildings in Europe are made of a variety of brick and stone masonry works, with strong critical issues concerning seismic hazard and architectural and/or functional rearrangements involving structural modifications. The latter activities frequently demand in situ investigations and structural analyses by which designers are requested, as in the case of Italian National Code, to carefully evaluate the effects of structural modifications and the need of retrofitting interventions. New openings in masonry walls are interventions often addressed, accompanied with local reinforcements, usually consisting of embedded steel frames, designed to grant no loss in terms of strength, stiffness and plastic capabilities. The present paper addresses the need of advanced numerical models assessing the behaviour of masonry walls under cycling loading, in presence of a new opening and of a reinforcing frame. For this purpose, a Finite Element (FE) model, accounting for plasticity and stiffness degradation, has been calibrated employing literature results from experimentations on real-size unreinforced rubble stone masonry (URM) walls subjected to shear cyclic loading (Vasconcelos and Lourenço, 2009). Thereafter the fine-tuned model has been employed for a numerical investigation on different configurations embedding a new opening and a reinforcing steel frame.