Research On The Connection Performance Of Domestic Metal-plate Joint In Domestic Larch Dimension Lumber

As a good structure material,the plantation larch distributes widely and grows fast.Domestic larch has been largely cultivated.The reasonable and effective utilization of domestic larch timber can effectively alleviate the status that structural timber in China mainly relies on imports.As a main connection form of the light wood truss,the connection performance of the metal-plate joint determines the safety and stability of the light wood truss.Development of domestic metal-plate,reasonable utilization of domestic dimension lumber and in depth study of the connection performance between domestic dimension lumber and domestic metal-plate were of great significance in improving the domestic light wood structure system.In this study,domestic larch dimension lumber and domestic metal-plate were collected as the research object.The ultimate bearing capacity,critical slip stiffness and failure forms,ductility and stress-strain changes in tensile process of the connected joint between the domestic metal-plate with indentation,domestic metal-plate with extension fringe tooth,domestic general metal-plate,imported M20 metal-plate and Larix kaempferi were analyzed.And the ultimate bearing capacity,critical slip stiffness,failure forms,ductility and stressstrain changes in tensile process of wood in different tree species and densities were studied.The main results and conclusions were summarized as follows:(1)The type of metal-plate had a great effect on the ultimate bearing capacity and the critical slip stiffness of metal-plate joints.In the configuration of AA(AE)type,The ultimate bearing capacity of imported M20 metal-plate was 1.06(1.12)times,1.36(1.46)times,1.42(1.47)times as large as domestic metal-plate,and The critical slip stiffness of imported M20 metal-plate was 1.09(1.18)times,1.11(1.19)times,1.11(1.31)times as large as domestic metal-plate.(2)The type of metal-plate had impacts on the failure modes and the ductility.The main failure modes of the imported metal-plate joint was the tooth with draw and wood damage,tooth pulled out and tooth root fracture were often happened in domestic metal-plate with indentation,tooth pulled out mainly happened in domestic metal-plate with extension fringe tooth and domestic general metal-plate.The ductility of domestic metal-plate joints was better than the imported metal-plate.In the configuration of AA(AE)type,the deformation that domestic metal-plate with indentation,domestic metal-plate with extension fringe tooth and domestic general metal-plate joints can bear were 1.01(1.18)times,1.21(1.66)times and 1.04(1.10)times as large as imported truss plate,the energy that joints can absorb were 1.15(1.25)times,1.81(1.56)times and 1.31(1.19)times as much as the imported metal-plate,respectively.(3)Species had a significant effect on the ultimate bearing capacity and The critical slip stiffness.The tensile strength of the three dimension lumbers,the domestic Larix gmelinii,Larix kaempferi and the imported Picea sitchensis were 158.93 MPa,137.57 MPa and 121.43 MPa,respectively.The ultimate bearing capacity,critical slip stiffness of the connected joints between two kinds of domestic larch dimension lumber and metal-plate with indentation were also higher than Picea sitchensis.In the AA(AE)configurations,the ultimate bearing capacity of Larix gmelinii and Larix kaempferi metal-plate connected joints were 69.42%(48.1%)and 4.71%(4.38%)higher than Picea sitchensis,and critical slip stiffness of them were 1.29(1.43)times and 1.20(1.32)times as large as Picea sitchensis.(4)Species had impacts on the failure modes and the ductility.The main failure modes of domestic metal-plate with indentation in three dimension lumbers are tooth with draw and wood damage,but in Larix kaempferi and Picea sitchensis,there would be root fracture phenomenon.Ductility of domestic Larch dimension lumber is better than that of Picea sitchensis.The deformation capacity and the absorption capacity of the connection joints of Larix gmelinii are higher than those of Picea sitchensis.The nodes of Larix kaempferi can undergo less deformation than the spruce trees,but the energy absorbed by the nodes was higher than that of Picea sitchensis.(5)Density had impacts on the connection performance of metal-plate joint.In the AA configuration,ultimate bearing force and critical slip rigidity of Larix kaempferi dimension lumber and domestic notch metal-plate node,increased with wood density,but the difference was not significant.The ductility of the connection joint of metal-plate decreased with wood density.The amount of deformation and energy absorbed by the metal-plate connecting joint of the low density timbers are 1.14 and 1.33 times as large as the medium density timbers and 15% and 8% higher than the low density timbers.In the AE configuration,the middle density timbers had the least ultimate bearing capacity,critical slip stiffness and ductility,but those of the high density timber were the highest.(6)Strain changes of the metal-plate.During the metal-plate node drawing process,the strains nearest to the center line of the toothed plate were higher than that of others,and had the highest tensile strength.Therefore,it most likely to reach yield strength and tooth withdraw.