Research On The Bending Mechanical Properties Of The Light Steel-Bamboo Folded Plate Fabricated Composite Beam

The construction industry has a huge amount of carbon emissions.With the implementation of the national strategic goal of "carbon peaking and carbon neutrality",the construction industry is facing a transformation and upgrading with the goal of low carbon and green.In order to build ecological,prefabricated and livable village and town houses,some scholars propose to use bamboo materials in building structures.The steel-bamboo composite structure can give full play to the advantages of the two materials: on the one hand,the bamboo can limit the local buckling of the light steel,and at the same time,the light steel makes up for the small elastic modulus of the bamboo,and achieves the combined effect of "1+1>2".In this paper,a new type of light steel-bamboo folded plate assembled composite beam is proposed.In order to fully study the failure mode,stress mechanism,bearing capacity and other properties of the composite beam,experiments,numerical analysis and design methods are carried out.The main content and The research results are as follows:(1)The material properties test of bamboo glulam was completed,and the tensile and compressive bearing capacity and elastic modulus of the parallel grain and horizontal grain were obtained.(2)Completed a four-point bending test including 19 composite beam members,the beam span is 2000 mm,and the test parameters are the type of flange(steel or bamboo),the width of the flange and the number of self-tapping screws.The analysis of the test results shows that the combination of pure bamboo form The bearing capacity of the beam is 150% and 71% higher than that of the pure steel and steel-bamboo composite beams,respectively;under the limit state of normal service,the bearing capacity of the two pure bamboo composite beams with flange widths of120 mm and 60 mm is small,so,the width of the pure bamboo composite beam can be appropriately reduced to achieve the goal of optimal design;the bearing capacity of the steel-bamboo composite beam connected by double nails is about 45% higher than that of the single nail connected composite beam;compared with Pure steel truss girder,steel-bamboo composite girder has greatly increased deformation at yield point and peak point with better ductility.(3)Completed four-point bending test of 25 steel-bamboo composite beams with a beam span of 3000 mm.The test parameters include shear-span ratio,composite beam width and height,web member type and thickness,etc.The analysis of the test results shows that the bearing capacity and the ductility coefficient decrease with the increase of the shear-span ratio;the design of the composite beam should adopt the side-compressed bamboo lamella web;the 30 mm thick web is used to connect the40 mm thicker webs with single nails.The bearing capacity of the plate single-nail connection is 22.61% higher,which is 13.45% lower than that of the 40 mm thick web plate with double-nail connection.In the optimization design,the thickness of the web should be reduced;compared with increasing the width of the composite beam,it is advisable to increase the composite beam beam height to increase the ultimate bearing capacity of the member.(4)The formulas for calculating the flexural bearing capacity and deflection of the normal section of the composite beam under four-point bending and uniform load are established.According to the test results,the application of the bamboo web increases the bearing capacity of the composite beam by 33%-45%.Therefore,the calculation coefficient of the bamboo web is introduced to properly modify the bearing capacity formula.The formula calculation results are close to the test results,and the error is small.And the influence of each parameter of the test against the change of bending stiffness is analyzed.(5)Using ABAQUS software,the numerical simulation study of double-nailed light steel-bamboo folded plate assembled composite beam was carried out.The failure modes,stress distributions and load-displacement curves of the specimens were compared with the experimental results.From the initial stage of loading to the failure stage of the structure,the established finite element model can better reflect the stress process of the composite beam,and the bearing capacity is in good agreement.