PRELIMINARY TEST RESULTS ON THE IN-PLANE STRENGTHENING OF TIMBER FLOORS WITH THE DOUBLE PLANKING TECHNIQUE

The seismic retrofit of existing masonry buildings often needs global interventions to guarantee the box-structural behaviour to inhibit the onset of local mechanisms. However, the so called box structural system requires a correct organization of the diaphragm, as well as its adequate connection to the masonry walls. The use of a new crosswise single layer of wooden planks is here proposed for the in-plane strengthening of existing timber floors. According to this solution, the new layer made with wooden planks has an inclination of 45° with respect to the existing ones that are arranged orthogonally to the wooden beams. The wall-to-floor connection is made of studs fixed to perimeter chord, which is in turn nailed to the wooden planks. The aim of this work is to highlight the role of the type and arrangement of the connections between the wooden planks and the steel plate on the shear behaviour of the diaphragm, as well as on the transmission of the actions from the perimeter chords to the diaphragm inner web-panel by means of an analytical model. The test results on in-plane cyclic shear behaviour of the diaphragm shows a linear trend of shear stresses along the plates, contrary to the usual design practice that assumes a uniform distribution.