Flexural behaviour of hardwood and softwood beams with mechanically connected GFRP plates

High performing, such as highly loaded, and large span hardwood and softwood beams are often used for industry, sports, public buildings or bridges, and provide an aesthetically pleasing and environmentally friendly structural solution. Reinforcement of wood beams may be required to extend the life of the structure due to deterioration or damage to the material or due to a change of use. In this paper, the flexural behaviour of hardwood and softwood beams reinforced by mechanically connected composite plates, has been studied through series of experimental investigations and analytical modelling. The use of GFRP (Glass Fiber Reinforced Polymer) composite strengthening, in the form of pultruded plates, can prevent tension failure in timber beams or highly reduce tensile stresses in beams under loading. The problem of reversibility, compatibility and poor performance at high temperatures of the “traditional” use of organic adhesives for reinforcement application has been solved by the use of mechanical connections. In detail, the experimental program included strengthening and testing 91 (50 made of hardwood and 41 softwood) simply supported square cross section small and full-scale beams. Each beam was loaded above its service load until complete failure. Different strengthening layouts and quantity of metal connectors were used. The increment in capacity and stiffness is the central focus of this paper and effects of strengthening on deflection, failure load and failure mode, strain, and hardwood beam ductility are discussed. A 3-dimensional (3D) finite element model is also presented for simulating the non-linear. Behaviour of GFRP-reinforced softwood beams. The ability of the numerical model to reproduce experimental results for the load-deflection curves is validated. The combination of different GFRP configurations together with a proper quantity of metal connectors, can lead to a doubling of the maximum load carrying capacity of the hardwood beam.