In-plane stiffening techniques with nail plates or CFRP strips for timber floors in historical masonry buildings

• Two strengthening techniques for timber floors in historical buildings are presented.
• CFRP strips or gang nails are utilised to enhance in-plane stiffness of timber floors.
• Simple relationships for designing strengthened floors are provided.
• The results of full-scale experimental tests on floor specimens are discussed.
• A masonry building with strengthened floors is analysed using a nonlinear FE model.

The paper investigates two strengthening techniques for timber floors in historical masonry buildings. These alternative solutions may be used to enhance in-plane stiffness and strength of existing wooden floors. According to the first technique, nail plates are utilised to connect adjacent timber boards, while diagonal carbon fibre (CFRP) strips glued to timber boarding are considered in the second solution. Four full scale stiffened floor samples, which were designed using specific relationships to calculate in-plane stiffness and resistance, were tested under in-plane cyclic loading. Test results showed an enhanced stiffness for strengthened floors which is 40–50 times higher than that of the original wooden floor and close to the values calculated employing the proposed design expressions. To study how the use of the analysed stiffening solutions affects the seismic performance of masonry buildings, nonlinear static analyses were carried out on a typical historical masonry building with wooded floors under earthquake loading. In particular, the response of the building with original floors was compared with that of the structure with strengthened floors. The numerical results confirmed that the stiffness of the reinforced floors is adequate to guarantee satisfactory structural integrity for the whole building as damage was found to be mainly located in shear walls, while walls perpendicular to earthquake loading remained almost undamaged.