Experimental and theoretical investigation of prestressed-steel-reinforced laminated bamboo lumber beams

This paper investigates a technique to strengthen laminated bamboo lumber (LBL) beams by embedding steel bars and prestressed steel bars at the specified locations. The flexural performance of the reinforced beams with different reinforcement ratios and levels of prestressing forces was investigated by studying the failure modes, load–displacement curves, load–strain curves, strain distribution at the critical cross-section and flexural resistance. Obtained experimental results showed that 85% of the beams failed due to the failure of bamboo fibers in the tension zone, and there was no significant failure in the compression zone. After embedding prestressed steel bars, the ultimate tensile and compressive strains of reinforced beam could reach up to 84% and 70% of those from the material test, respectively. The load capacity of both steel-reinforced beams and prestressed-steel-reinforced beams was significantly increased, with a maximum load capacity of 60% higher than the ordinary beams. In addition, both steel-reinforced beams and prestressed-steel-reinforced beams showed significant improvements, 40% and 49% respectively, in flexural resistance when compared to that of the ordinary beams. Theoretical equations for predicting flexural resistance of strengthened LBL beams have been proposed based on the observed strain and stress distributions.