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

Wood structure building has a long history in China.Since the founding of the People’s Republic of China,the new buildings have been mainly reinforced concrete structure,and the development of wood structure has been in a stagnant stage.Recent,because of the popularity of the concept of environmental protection,as well as the advantages of wood structure,such as heat preservation and insulation,excellent seismic performance and green renewable materials,wood structure buildings are more and more popular.Actuality,the lack of high-quality wood in our country limits the development of wood structure,but the fast-growing poplar in our country has a wide range of distribution and large output,but its application range is small due to its loose structure and low strength.In order to widen the application scope of fast-growing poplar,the fast-growing poplar can also be used in building structure to modify the fast-growing poplar.The paper includes the following aspects.(1)Through the bending test of one original wood beam and three glued reinforced wood beams,the bending performance and stress mechanism are obtained.The experimental results show that the load-bearing capacity and bending rigidity of the fast-growing poplar can be significantly improved by using the structural adhesive to strengthen the timber beam,and the specimen still shows the characteristics of brittle failure when it is damaged.The size effect exists in the modified glued wood beams with different sizes,and the strength of the specimens with larger section size decreases.(2)The ultimate bearing capacity and bending rigidity of the specimen can be improved significantly by steel plate.When a steel plate is arranged at the bottom of the wood beam,the ultimate bearing capacity of the test piece is closely related to the steel ratio of the wood beam.With the increase of the steel ratio,the bearing capacity of the modified quick-growing poplar beam increases first and then decreases.When a steel plate is arranged in the tension area and the compression area respectively,the change range of bearing capacity of the test piece with changing the thickness of the steel plate is small,indicating that the steel ratio has little influence on the bearing capacity when a steel plate is arranged in the upper and lower parts of the test piece.When steel plates are arranged in different positions,the more steel plates are arranged,the greater the ultimate bearing capacity and bending rigidity of the modified fast-growing poplar beams are.(3)The flexural rigidity and ultimate bearing capacity of the fast-growing poplar beam strengthened by carbon fiber cloth are significantly improved.At the later stage of loading,the specimen still shows the characteristics of brittle failure.The ultimate bearing capacity and flexural rigidity of the specimens increased in the tensile zone,while the bearing capacity of the specimens in the compression zone decreased slightly.