Experimental study of flexural behavior of glulam Douglas Fir beams spliced with engineered bamboo cover plates and inclined self-tapping screws

Abstract

Due to the limitation of transportation and installation, long-span timber structural components need to be extended through multiple spliced joints. Among the common spliced joints, spliced beam joints with self-tapping screws have the advantages of low cross-section weakening, beautiful appearance, and convenient construction. However, the beam joints spliced by self-tapping screws have limitations in terms of bearing capacity and stiffness. To overcome these limitations, this paper proposes inclined self-tapping screw-engineered bamboo joints. In this novel joint, the high-strength engineered bamboo connection plates are used to improve the mechanical properties of spliced glulam beams. A total of thirteen glulam beams were designed. The effects of the layout and number of self-tapping screws, types of connection plates, and spliced gaps on the flexural performance of novel glulam beams were experimentally investigated through four-point bending tests. The results show that the mechanical properties of the spliced beam with parallel self-tapping screws are better than those with staggered self-tapping screws. The bending capacity of the glulam beams spliced with bamboo scrimber plates arranged in parallel increases with the increase of the number of self-tapping screws. The average bending capacity and stiffness can reach 97.3 % and 93.3 % of the intact beams, respectively. The bending capacity and stiffness of glulam beams with the same number of self-tapping screws arranged in parallel and spliced with plybamboo are lower than those of glulam beams spliced with bamboo scrimber. The gap between the spliced cross-sections of glulam beams significantly reduces the flexural mechanical properties of spliced beams, especially the stiffness.