Abstract
The fiber-reinforced polymer is one kind of composite material made of synthetic fiber and resin, which has attracted research interests for the reinforcement of timber elements. In this study, 18 glued-laminated (glulam) beams, unreinforced or reinforced with internally embedded carbon fiber–reinforced polymer (CFRP) sheets, were tested under four-point bending loads. For the reinforced glulam beams, the influences of the strengthening ratio, the modulus of elasticity of the CFRP, and the CFRP arrangement on their bending performance were experimentally investigated. Subsequently, a finite element model developed was verified with the experimental results; furthermore, a general theoretical model considering the typical tensile failure mode was employed to predict the bending–resisting capacities of the reinforced glulam beams. It is found that the reinforced glulam beams are featured with relatively ductile bending failure, compared to the brittle tensile failure of the unreinforced ones. Besides, the compressive properties of the uppermost grain of the glulam can be fully utilized in the CFRP-reinforced beams. For the beams with a 0.040% strengthening ratio, the bending–resisting capacity and the maximum deflection can be enhanced approximately by 6.51 and 12.02%, respectively. The difference between the experimental results and the numerical results and that between the experimental results and analytical results are within 20 and 10%, respectively.
Highlights
The mechanical properties of timber elements can be significantly influenced by the presence of natural defects
All the bending failure belongs to a brittle failure mode, whereas some slight distinctions existed in the specific destruction phenomena between unreinforced glulam beams and carbon fiber–reinforced polymer (CFRP)-reinforced glulam beams
According to test results presented an fiber-reinforced polymer (FRP) sheet with a lower tensile strength is recommended for the FRP-reinforced glulam beams
Summary
The mechanical properties of timber elements can be significantly influenced by the presence of natural defects (e.g., knots and cracks). For the historical timber buildings, their key structural components commonly require repairing and reinforcing in modern times; besides, for the modern timber buildings, the increasing demands for both higher strength and stiffness of their structural members would facilitate the application of the reinforcing technology. Timber members reinforced with steel materials have been widely studied (McConnell et al, 2014; Wei et al, 2020; Zhang et al, 2020), whereas their applications were limited due to the relatively high density and poor corrosion resistance of the steel reinforcement materials. An increasing number of investigations have been conducted on reinforcing timber structures with fiber-reinforced polymer (FRP), owing to its excellent resistance to corrosion, high strength-to-weight ratio, and the diversity of FRP products (Sun et al, 2020).
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