Mechanical Response of Timber Beams Strengthened with Variable Amounts of CFRP and Bamboo Scrimber Layers

Abstract

This paper proposes a novel method for strengthening existing timber beams that can effectively improve the deformability of beams. As high-performance engineered bamboo, bamboo scrimber was attached to the bottom tensile area of a timber beam together with carbon fiber–reinforced polymer (CFRP) layers. The CFRP was used to improve flexural strength, and the bamboo scrimber was used to enhance the flexural stiffness and strength of the original timber beams. Fourteen timber beams were tested to study the flexural behavior of the reinforced timber beams. The main test parameters included the bamboo scrimber thickness and the number of CFRP layers. The results showed that the stiffness and bending strength of the beam increased with the increasing thickness of the bamboo scrimber, but no noticeable effect was observed with the addition of the CFRP layers. The cross-sectional stiffness at the serviceability limit state and ultimate bending strength increased by approximately 70%–130% and 50%–90%, respectively. A stable and durable platform segment was observed for most reinforced beams, which displayed excellent deformability. The large deformable behavior was mainly due to the fact that the addition of bamboo scrimber delayed the tensile failure of the wood, and timber under compression parallel to the grain showed plastic behavior. By considering the simplified stress–strain relationship for the constituent materials and force equilibrium in the cross section, an analytical strength model was developed for predicting the flexural capacity of timber beams reinforced with bamboo scrimber.