Experimental Study On Flexural Properties Of Side-Pressure Laminated Bamboo Beams

With the rapid development of China’s economy,the demand for traditional building materials such as steel and concrete has increased dramatically,which has a serious impact on the ecological environment.Therefore,"green building" has become an important issue of concern to the whole society.Compared with the traditional building materials(concrete,steel,etc.),the laminated bamboo is easy to degrade,renewable and light in weight.It is an ideal green high-strength building material.side-pressure laminated bamboo is a kind of building structural material with excellent mechanical properties,which has the advantages of good rigidity,high strength,stable performance,good seismic performance,etc.However,at present,there is a lack of relevant design codes and standards for the construction of bamboo skidding at home and abroad,which limits the promotion of bamboo skidding in the project.At present,the research on the flexural members of side-pressure laminated bamboo is still in its infancy and grope stage,and the mechanical properties,failure mechanism,mechanical calculation model,bearing capacity and deformation need to be further studied.In this paper,through experimental research and theoretical analysis,the bending performance and creep performance of the lateral pressure side-pressure laminated bamboo beam are studied in depth.The main research work and results are:(1)Experimental study on the flexural capacity of side-pressure laminated bamboo beam.Considering the height width ratio and the span height ratio,five groups of 10 side-pressure laminated bamboo beam were designed.The flexural capacity tests were carried out to study the flexural performance of the members.The failure mode,load displacement relation curve and the change rule of strain of midspan section with height are obtained by experiments.The results show that the stress process of the side-pressed bamboo integrated beam has undergone the elastic deformation stage,elastoplastic deformation stage,and the failure stage;the beam mid-span deflection when the beam specimen is broken has far exceeded the maximum allowable value specified in the code.In the design process of side-pressure laminated bamboo beam,the stiffness or deflection should be used as the control index.As the width of side-pressure laminated bamboo beam increases,the bearing capacity increases substantially with the beam width,and the average strain of the section basically conforms to the plane section assumption.(2)Study on the long-term mechanical properties of side-pressure laminated bamboo beam.The test beams are divided into three groups of F1,F2,and F3 according to different loading stresses,and the four-point bending loading method is used for long-term loading tests under normal use conditions.The load values of F1,F2 and F3 are 30%,45%and 60%of the standard value of ultimate bearing capacity respectively.The long-term load test of each group of beams has been carried out for 8 months,and the test data of long-term creep deformation of side-pressure laminated bamboo beams has been obtained.The change rule of deflection with time in the long-term load process has been studied,and the influence of long-term load on the long-term bending performance of side-pressure laminated bamboo beams has been obtained.It can be seen from the test that the stress level has an important influence on the creep deformation of the side-pressure laminated bamboo beam.The stress level is low and the creep deformation degree is relatively small.When the loading level is higher than the normal service load,the development of the creep deformation is more obvious;The side-pressure laminated bamboo beam is unstable and damaged under the long-term load of high stress level,so the creep deformation under the long-term load should be considered in the engineering design;The maximum deflection of the test beam in the middle of the span has far exceeded the maximum allowable value specified in the code,so in the actual engineering design,the normal use of the side-pressure laminated bamboo beam can be considered to design with the rigidity or deflection as the control index.(3)Study on the calculation formula of the flexural capacity of the side-pressure laminated bamboo beam.Based on the plane section assumption and the material stress-strain constitutive relation,the ultimate flexural bearing capacity formula of the side-pressure laminated bamboo beam is derived,and the simplified calculation formula of the flexural bearing capacity is proposed.The calculation results are in good agreement with the test results.(4)Study on bending stiffness of the side-pressure laminated bamboo beam.Based on the results of the material property test and considering the nonlinear characteristics of the side-pressed bamboo laminated timber material,the relationship between the bending moment and stiffness of the side-pressure laminated bamboo beam was established based on the plane assumption of the beam section,and the stiffness calculation formula of the beam is proposed.The short-term bending deformation and long-term deformation calculation formula are also established.The calculation results are compared with the test results good agreement.