Traditional timber floors in masonry buildings are characterized by very low in-plane stiffness and lack of effective connections to the main walls, so the structure seismic performance is negatively affected and reinforcement of timber floors is often needed. In this paper, in-plane dry strengthening solutions for timber floors in existing masonry buildings are faced: in particular CLT panels were connected to traditional timber floors and tested. The solution is reversible, not invasive and ensures a limited increase of the seismic mass. Experimental tests are performed on full-scale unreinforced and reinforced floors, under in-plane cyclic loading. The tests show a significant increase in shear strength and stiffness of the strengthened floors with respect to the unreinforced ones. Test data can be useful also for a reliable modeling of the floors in plane strength, as experimental data are still very few. A first approach to the study of the relationship between the diaphragm behaviour and unreinforced masonry building seismic response is reported. Numerical simulations on a simple masonry box structure under seismic loads are carried out using the Discrete Element Method. The comparison with the rigid diaphragm case confirms the good performance of the proposed strengthening solution.
