Experimental Study On Flexural And Shear Behavior Of Short Modified Fast-growing Poplar Beams

In recent years,due to the restriction of commercial logging in natural forests and the expansion of the gap between supply and demand of wood resources in China,artificial fastgrowing forests have gradually become the development trend of the wood industry.As one of the three fast growing species in China,fast-growing poplar not only has the advantages of strong adaptability,wide planting range and short growth cycle,but also has the defects of low wood fiber content,many wood joints and poor mechanical properties.In order to promote the application of fast-growing poplar wood in green building,this paper proposes the lamellar composite modification of fast-growing poplar beams with structural adhesive,steel plate and carbon fiber cloth.Through the bending test of the modified fast-growing poplar short beam specimens,the following studies were carried out in view of the changes in the bearing capacity,deformation capacity and failure state of the specimens:1.In this paper,the bending tests were carried out on the specimen modified with structural adhesive,which were made of the fast-growing poplar and two-component structural adhesive.Through the experimental analysis of 2 short beams specimens,the influence of laminate modification on the mechanical properties of the modified specimens was investigated.The results show that,compared with fast-growing poplar logs specimen,the load-bearing capacity of the specimens modified with structural adhesive is not significantly improved,but the stiffness of the specimens is increased,and the brittleness is damaged by bending when the specimens are damaged.2.In this paper,the bending tests were carried out on the specimen modified with steel plate,which were made of the fast-growing poplar plate,steel plates and structural adhesive.Through the experimental analysis of 19 short beam specimens in 5 groups,the influence of thickness of fast-growing poplar laminate,shear span ratio of specimens,number of steel plates and arrangement position on bending shear performance of the modified specimens was investigated.The results show that,compared with fast-growing poplar logs specimen,the bearing capacity and stiffness of specimens modified with steel plate were significantly improved.The smaller the shear span ratio,the more obvious the shear failure.The bearing capacity of specimens is closely related to the thickness of fast-growing poplar wood.3.In this paper,bending tests were carried out on the specimen modified with carbon fiber cloth,which were made of fast-growing poplar wood,carbon fiber cloth(0.167 mm thick)and structural adhesive.Through the experimental analysis of 5 short beam specimens,the influence of the quantity and arrangement of CFRP sheets on the bending shear performance of the modified specimens was investigated.The results show that,compared with fast-growing poplar logs specimen,the load-bearing capacity of specimens modified with CFRP has been significantly improved.The number and position of CFRP arrangement have a great influence on the bearing capacity and failure state of the specimens.4.Based on the assumption of plane section,constitutive relation of specimen material and experimental value,the formulae for calculating the flexural and shear capacity of modified fast growing poplar beams are derived in this paper.