| The bamboo scrimber is an advanced composite material which is processed into bamboo strips by dipping,drying,molding,high temperature and high pressure thermal curing.It has the advantages of high utilization rate,excellent mechanical properties.As a building structural material,the bamboo scrimber structure has short construction period and good seismic behavior,and has been gradually applied in the building structural system at home and abroad.However,due to the low elastic modulus of the bamboo scrimber,the deflection changes greatly during bending and the bamboo fiber is prone to brittle fracture under tension,the application scope of the scrimber bamboo in long-span structures is limited.Therefore,it is necessary to improve the bending performance of the bamboo scrimber flexural members by means of a combination structure.Compared with steel,aluminum alloy has the advantages of light weight,high strength,corrosion resistance,good ductility and so on.It is the second largest metal material used in the world.In view of the comprehensive advantages of aluminum alloy materials,the bamboo scrimber-aluminum plate composite beam is formed by combining aluminum alloy plates with the tensile zone of the composite bamboo beam through adhesives and screw connection.At present,there are few relevant design specifications for bamboo scrimber structures and need to be improved.Because the flexural members mainly bear bending moment and shear,it is necessary to study the basic mechanical properties of bamboo scrimber under the condition of bending and shear,and to explore the mechanical properties of the bamboo scrimber-aluminum plate composite beams.Based on the basic mechanical properties tests of each group of 40 bamboo scrimber under condition of bending,shearing parallel to grain,shearing perpendicular to grain,shearing in transverse to grain plane,and12 bamboo scrimber-aluminum plate composite beams.By using the finite element analysis software,mechanical properties of bamboo scrimber under shearing and bending,and the mechanical properties of bamboo scrimber-aluminum composite beams have been studied in the following aspects:1.The bending failure mode and failure mechanism of bamboo scrimber were analyzed,and the eigenvalue of mechanical parameters were extracted.By fitting data,the conversion formula between flexural strength,flexural elastic modulus and shear strength of bamboo scrimber was put forward.2.The failure mode and failure mechanism of bamboo scrimber under shear in different fiber directions were analyzed.According to the different failure modes of the specimens,the corresponding stress-strain relationship model was established,and the eigenvalue of the shear mechanical properties of the bamboo scrimber were extracted.3.Using the finite element software,the finite element model of bamboo scrimber-aluminum plate composite beams are established.In order to verify the reliability of the model,the load-displacement curve of the finite element model is compared with the test results.On this basis,the yield strength of aluminum plate,thickness of aluminum plate,shear strength of adhesive,shear span ratio and height width ratio are taken as parameters to analyze the finite element model of composite beams,and study the influence law of various parameters on the bending performance of composite beams.4.By means of the superposition method,the bending stiffness calculation formula of the composite beams are derived.By comparing the theoretical calculation value with the experimental value,the bending stiffness reduction coefficient is presented.5.Based on the elastic theory,considering the shear deformation of the composite beams,the calculation formulas of the mid span deflection and bending capacity of the composite beams on serviceability limit state are derived.The calculation results of the formula are compared with the test results and the finite element calculation results,and the correctness of the formula is verified.6.According to the elastic-plastic theory,considering the influence of shear slip on the flexural capacity of composite beams,and combining with the results of finite element analysis,calculation formulas of bending capacity of the composite beams on ultimate limit state are derived.The calculated values of the formula are in good agreement with the experimental results and the finite element calculation values. |
