Flexural Behaviour of Glulam Beams and Joints Reinforced With CFRP Bars: Theoretical Analysis

Glulam structural members present lightweight, absence of corrosion and good mechanical properties even if they have high deformability due to flexural and shear stresses. In order to fulfil design requirements high cross sections are often necessary, therefore the volume of the structures increases as same as the transport costs. Carbon fibre polymer (CFRP) rods may be used as near-surface glued-in flexural reinforcement in order to increase the strength and stiffness of glulam beams with low dimensions of the cross section. In this study the results of mechanical tests on unreinforced and CFRP-reinforced flexural glulam beams are reported and compared to a numerical model based on elastic beams theory. Glulam specimens, five meters long, were reinforced with two different amounts of CFRP rods that were bonded on the tension side of the beams with an epoxy resin. A good accordance was found between theoretical and experimental results in terms of load vs deflection curves. load vs strain curves, carrying capacity and failure modes. A theoretical study is also presented herein in order to predict the flexural behaviour of CFRP-jointed glulam beams. The proposed model aims to compute the load vs deflection curves for an innovative system that uses CFRP rods in place of traditional steel fasteners in order to transmit flexural stresses between two head-jointed beams. The mechanical behaviour was modelled in analogy of a reinforced concrete section, taking into account the elastic properties of the used materials; the deflection was computed using the virtual work theory, and taking into account the contributes due to flexural and shear forces, and to the rotational deformability of the CFRP epoxy-bonded joint. The results that were found can be assumed as a useful basis for future guidelines that are necessary for designers and practitioners, even if further experimental studies are needed in the field.