Length effect on bending properties and evaluation of shear modulus of parallel bamboo strand lumber

摘要

One hundred sixty-two parallel bamboo strand lumber (PBSL) beams were tested for the bending properties under three-point bending with variable span. Two typical failure types were classified, type I was tension failure of the bamboo fiber located below the neutral axis at mid-span, while type II was shear failure which was mainly found in specimens with large depth-span ratio. The shear modulus G(LR )of PBSL was also calculated according to Timoshenko's bending theory. To evaluate the shear modulus, 45 degrees off-axis compression tests had been done. The results showed that the mean values of shear modulus for G(LT), G(TR), and G(LR) are 1254.5 MPa, 408.1 MPa, and 716.4 MPa, respectively. The bending test result was compared with the shear modulus measured by 45 degrees off-axis compression test. It was found that the shear modulus measured by three-point bending test with variable span was significantly less than the shear modulus obtained by 45 degrees off-axis compression test. The empirical equation of shear factor s corresponding to depth-span ratio h/l was proposed. The calculation results gained from the proposed formula are in good agreement with the 45 degrees off-axis compression test results.