Experimental and theoretical investigation of short-term behavior of unbonded prestressed bamboo scrimber-steel composite beams

Abstract

This paper investigates a novel unbonded prestressed bamboo scrimber-steel composite beam by embedding steel tubes within bamboo scrimber to form channels, through which steel bars are threaded and prestressed after shaping. Four-point bending tests were conducted to evaluate the effects of reinforcement ratio and prestress level on the short-term flexural behavior of the beam. The failure modes, load-midspan deflection, ultimate bearing capacity, stiffness, and strain distribution of the beams were analyzed based on the experimental data. The test result showed bamboo scrimber beams strengthened with steel with a reinforcement ratio ranging from 1.84 % to 5.23 % experienced a significant increase in ultimate bearing capacity of 5.64∼29.09 % and an increase in flexural stiffness of 5.71∼24.31 %. Flexural stiffness increases with the reinforcement ratio. Enhancing both the reinforcement ratio and prestress level effectively improves ultimate bearing capacity. However, as the reinforcement ratio increases, the impact of increasing the prestress level on improving ultimate bearing capacity diminished. Based on the deformation model of unbonded prestress bars, a theoretical model for the ultimate bearing capacity of the unbonded prestressed bamboo scrimber-steel composite beams was established. The calculated value of the bearing capacity was in good agreement with the test results.