Length effects on combined tension-bending properties of bamboo scrimber

Bamboo scrimber (BS), as a green and low-carbon building material that shows great potential for application in the construction field, is required to cope with complex combined tension-bending (CTB) loading conditions when employed as a beam structure. The issue of how dimensional factors affect the mechanical properties of BS under complex loading conditions has not yet been fully clarified. In view of this research gap, in this study, CTB tests were conducted on BS specimens with different gauge section length L-0 (50 mm similar to 200 mm) at a large range of pre-tension force F-pre (0-4500 N). The experimental results show that the changes of F-pre and L-0 have a significant effect on the mechanical response of BS. Specifically, the maximum bending force, effective flexural modulus, and total dissipated energy of the BS increased significantly with the enhancement of F-pre and the extension of L-0. However, these positive effects are accompanied by a decrease in ultimate strain. In addition, as F-pre increases with L-0, the location of fracture occurrence exhibits greater randomness. Fracture analysis by Scanning Electron Microscope (SEM) showed that F-pre and L-0 had significant effects on the fracture mechanism. With the increase of F-pre and L-0, the fracture mode transforms from fiber pull-out dominant to fiber fracture dominant. This study not only deepens the understanding of the mechanical behavior of BS under complex loads but also can provide valuable experimental data and theoretical support for its safe application in building structure design.