Flexural strengthening and stiffening of ancient wooden floors: a new technique

A strengthening technique for the wooden floors of historical buildings aimed to increase both flexural and in-plane stiffness is herein proposed. The technique, which is highly reversible and little invasive, consists in placing steel plates above the existing boarding and in connecting them to the wooden beams by means of steel dowels. Finally, a system of diagonal steel strips welded to perimetric steel profiles anchored to the walls, stiffens the floor in its plane in order to guarantee an effective seismic behaviour. In the paper the results of experimental investigations on the connection between the steel plates and the wooden beams and the outcomes of load tests on existing floors before and after the strengthening intervention are presented. A numerical model for the strengthened floors has also been developed by using the experimental outcomes. Numerical analyses on both strengthened beams and a whole ancient masonry building with wooden floors have been carried out. The results achieved show the effectiveness of the proposed strengthening technique regarding the improvement of the out-of-plane floor stiffness and the load bearing capacity as well as the enhancement of the seismic performance of the analyzed ancient masonry building whose floors have been strengthened. It has been proved that the strengthened floor’s in-plane stiffness is fifty times higher than that of the original floor and furthermore, that the seismic resistance of the building, whose floors have been strengthened, is approximately fifty per cent higher than that of the original structure.