Study On Flexural Properties Of Bamboo-Timber Composite Beams

Timber is a renewable green construction material.Moreover,the span and flexural capacity of traditional timber structures are sensitive to many factors such as material characteristics.To improve the poor bearing capacity of timber structure and low utilization rate of timber,three types of bamboo-timber composite beams,including bamboo-long timber composite beams,bamboo-short timber direct splicing beams and bamboo-short timber lap joint beams,were manufactured with domestic Pinus sylvestris var.mongolica and widely distributed bamboo as raw materials and two-component epoxy resin adhesive as adhesives.The shear test of adhesive specimens,compression test of wood and tension test of glue-laminated bamboo were carried out,and then the flexural properti'es of bamboo-timber composite beams and timber beams were compared.The flexural capacity,effect of knag distribution and displacement ductility of the beams were studied.The formulas for calculating flexural capacity were deduced,and the economic analysis was carried out.Finally,ABAQUS finite element modeling analysis was applied to provide reference for the design of timber structures.The main research results are as follows:(1)Through the experimental study on flexural property of 12 rectangular cross-section beams.The stress and deformation data of the specimens was obtained,and the bending deformation properties and the bending failure mechanism of the specimens was revealed.The test results show that all the specimens have brittle failure.Compared with wood beams,the bending capacity of bamboo-long timber composite beams increases by 55.7%,the bending stiffness also increases greatly,the displacement ductility increases,and the reinforcement effect of glue-laminated bamboo is remarkable.At the same time,it is found that the influence of knots in tension zone is relatively small.The bending properties of bamboo-short timber direct splicing beams and bamboo-short timber lap joint beams with different connection modes are comparable to those of timber beams,but the bamboo-short timber lap joint beams are better.(2)The experimental results show that the bending deformation of bamboo-timber composite beams conforms to the assumption of plane section.Based on this,the formulas for calculating the flexural capacity of such beams was derived.The theoretical results were in good agreement with the experimental results.The recommended height of reinforced section of glue-laminated bamboo was given when the balance failure of bamboo-long timber composite beams occured.Through the univariate linear regression analysis,the economy of all kinds of specimens was evaluated,and the cost of the bamboo-short timber lap joint beam could be saved.(3)The flexural behavior of bamboo-timber composite beams was analyzed by finite element method,and the numerical model of bamboo-timber composite beams was established.The stress distribution and load-displacement curves were obtained.The numerical results were compared with the experimental results,and they were in good agreement.The reliability of numerical analysis of bamboo-timber composite beams by ABAQUS finite element analysis software was verified.