No abstract

To improve the bending performance of long-span bamboo scrimber beams, a new method of prepressing-cold pressing-hot forming was used to produce steel-reinforced bamboo scrimber composite beams. For steel-RBSC beams, four-point bending experiments were performed to study the failure mode, bending performance, load-displacement relationships, and strain history curves of composite beams. Based on cohesive zone model theory, finite element models of steel-RBSC beams were established and the bonding stress of the adhesive layer in steel-RBSC beams revealed. The results indicated that the failure mode of composite beams was fracture failure of the bamboo scrimber at the bottom between the loading rollers. Steel reinforcement had a significant effect on the strength and stiffness of bamboo scrimber beams. The maximum static stiffness of composite beams was increased by 70.15%, compared with that of bamboo scrimber beams. The load-displacement curves, mechanical properties, and section strains predicted by finite element models were consistent with the test results, verifying that these finite element models were correct. The main influence factors for the peeling of the adhesive layer were normal stress, shear stress, and mixed stress in the areas of pure bending section, bending-shear section, and loading roll area, respectively.

In order to study the long-term tensile creep properties of bamboo scrimber, this paper conducted long-term tensile creep tests in parallel-to-grain of bamboo scrimber in the indoor environment, and studied the creep failure mode, creep strain and creep compliance of bamboo scrimber in the long-term tensile. Furthermore, we proposed a unified creep life prediction method at the full stress level. The method included fitting the theoretical model of creep compliance of bamboo scrimber under long-term tension by using the multi-branch Kelvin-Voigt model, fitting the shear relaxation model in the form of Prony series by using the multi-branch generalized Maxwell model, establishing the creep finite element model of the bamboo scrimber specimen in the parallel-to-grain tension, and establishing the creep life prediction model of the bamboo scrimber in the parallel-to-grain tension based on the creep failure rule and the creep deformation data calculated by the finite element model. The results showed that the creep strain curve of bamboo scrimber included unstable creep stage and stable creep stage without accelerated creep stage. The specimen broke instantaneously in the last 1 second, and the fracture shape showed as flush fracture and oblique fracture. Under 70% of the ultimate load level, the creep characteristics of the bamboo scrimber in the parallel-to-grain tension were linear viscoelastic, and the creep compliance was basically independent of the load level. The creep finite element model of bamboo scrimber tensile specimen could accurately calculate the creep deformation of the bamboo scrimber. The creep life prediction model could accurately predict the creep life of bamboo scrimber at the full tensile stress level in parallel-to-grain.