Viscoelastic creep in reinforced glulam

The mechanical and physical properties of softwood timber can vary considerably as a result of the age and rate of growth of the tree and other environmental factors which affect the wood cell density and strength [1]. Sitka spruce is characterised as a fast growing, low density timber which when subjected to flexural loading generally fails in tension due to the presence of knots [2].When combined to create a composite element such as a glued laminated beam, the capacity of this softwood timber may be greatly increased. The short-term stiffness of these fast-grown glued laminated beams has been shown to further benefit from the addition of a fibre reinforced polymer (FRP) material of superior properties [2]. The effect of this FRP reinforcement on the long-term performance of these beams requires attention [3]. Currently, there are no long-term creep factors defined in design codes for reinforced timber elements, which prevent structural engineers and designers from utilising the increase in stiffness provided by reinforced elements. This study aims to investigate the long-term creep behaviour of timber elements reinforced with basalt fibre reinforced polymer (BFRP) rods and compare the results to similar beams in their unreinforced state.