Masonry buildings are highly vulnerable to seismic loading and their dynamic response is strongly influenced by the timber floors in-plane deformability and by the quality of the wall-to-floor connections. Understanding the behaviour of timber floors and roofs and their interaction with the masonry walls is therefore fundamental for the protection of historical buildings. In a previous research project, different timber-based dry-connected strengthening solutions for timber floors were tested under in-plane loads. The experimental results show a significant increase in shear strength and stiffness.

The Discrete Element Method is here used first to model a simple masonry structure and to evaluate the effectiveness of the strengthening solutions in avoiding the triggering of the “1^st mode” mechanisms (out-of-plane collapse of masonry walls) and after to evaluate the behaviour of a listed masonry building.

Different models of the cyclic behaviour of the floors were also applied in the two cases.

In the simple masonry structure the unreinforced and reinforced floors are modelled by beams connected with non-linear springs that reproduce their experimental hysteretic response. Parametric analyses are performed, changing the geometry of the structure and the masonry wall thickness.

A simpler, previously developed, model of the floor cyclic behaviour is applied herein to DEM models of the listed masonry building.

In both the analyses the results highlight the effectiveness of the floor strengthening solution in reducing the out-of-plane displacements of masonry walls. With adequate connections, the reinforced floor is able to transfer the seismic forces to the shear-resistant walls up to the shear-sliding collapse of the structural sidewalls. A comparison with the ideal rigid diaphragm case confirms the good performance of the strengthened floors. The small observed out-of-plane displacements are compatible with the masonry wall capacity, and the reinforced floor hysteretic cycles contribute to dissipate part of the input energy. Moreover, different designs of the connections can also cap the transferred seismic forces to an acceptable level for shear-resistant walls.