Experimental Research And Theoretical Analysis On Tensile Properties Of Laminated Bamboo Self-tapping Screw Connection

Green ecological material——the laminated bamboo has good mechanical properties,it can be used as building structural materials.Because the bamboo and wood structure is a prefabricated structure,the joint connection mode of the load-bearing members is always the key problem.The laminated bamboo adopts the connection mode of self-tapping screw,which has reliability and convenience.In this paper,the tensile properties of laminated bamboo self-tapping screw joints are studied to explore the joint failure mode of laminated bamboo self-tapping screw joints under tension and reveal the failure mechanism of laminated bamboo self-tapping screw joints.The main research results of this paper are as follows:(1)The failure mechanism of the laminated bamboo self-tapping screw connection is discussed through the tensile performance test.This section mainly studies the influence of different thickness and grain direction of laminated bamboo plates on the self-tapping screw connection,and concludes that with the increase of laminated bamboo plate thickness,the ultimate load,yield load and ductility of the specimen will increase,and the initial stiffness increases first and then decreases.Through the experimental analysis of different grain directions of laminated bamboo,it is concluded that the effect of grain directions on the mechanical properties of joints is not significant.In addition,there are two main failure modes of laminated bamboo self-tapping screws,one is the local pressure failure to achieve the bearing strength of the plate,and the other is the splitting failure in parallel grain direction.(2)The variation of the withdrawal capacity of the laminated bamboo self-tapping screw was studied through the withdrawal capacity test of the laminated bamboo self-tapping screw.In this section,the relationship between the Angle of self-tapping screws and the grain direction of laminated bamboo,the anchoring length of self-tapping screws and the withdrawal bearing capacity of specimens is studied.The results show that the withdrawal bearing capacity of specimens increases with the increase of the Angle of self-tapping screws and the grain direction of laminated bamboo.By studying the anchoring length of self-tapping screws,it is concluded that with the increase of anchoring length,the withdrawal strength of specimens increases.There are three main failure modes of the joints,self-tapping screw pulling failure,shear failure along the grain direction and self-tapping screw breaking failure.(3)The theoretical analysis model of the withdrawal bearing capacity of the laminated bamboo self-tapping screw is established,and the reliability of the model is verified by the test results.Through the linear elastic finite bond line shear stiffness approach,the calculation formula of the withdrawal bearing capacity of the laminated bamboo self-tapping screw is obtained,and the theoretical value of the withdrawal bearing capacity of the laminated bamboo self-tapping screw is calculated according to this formula,and the theoretical model is verified by comparing with the experimental value.