| With the healthy and comfortable lifestyle has become the trend of this time,the environmentally-friendly,healthy and comfortable wood construction is gradually popular.The wood light-frame construction from North America was introduced into China with its high-strength lightweight,energy conservation,environment friendly and high construction efficiency.However,wood construction materials in China mainly relied on imports at present due to the lack of appropriate domestic building materials.For these reasons,the development of domestic specifications and metal connectors that suitable for wood light-frame construction can be a very valuable work.Larix kaempferi(Lamb.)Carr.is an important specie in North China,with good mechanical properties,corrosion resistance,straight trunk,etc.It distributes widely and has large storage.Thus,it is of great significance to develop domestic Larix kaempferi(Lamb.)Carr.dimension lumber in wood light-frame construction.In this paper,the domestic Larix kaempferi(Lamb.)Carr.dimension lumber and the domestic truss plate were collected as experimental materials.The lateral resistance of teeth,tension resistance and shear strength were obtained by tension test and shear test.The design value of lateral resistance of teeth,tension resistance and shear strength were calculated by the strength adjustment coefficient of the truss plate that was obtained by the test of the steel material property.The static load-carrying test of six kinds of parallel chord light wood trusses was carried out under two loading case.The main results and conclusions were summarized as follows:(1)The load-carrying capacity of the joints between the domestic truss plate and Larix kaempferi(Lamb.)Carr.dimension lumber was studied,and the test value of the lateral resistance of teeth under the four styles,AA,AE,EA and EE,were 1.66 N/mm~2,1.13 N/mm~2,1.19 N/mm~2 and 1.12 N/mm~2,respectively.The test value of tension resistance when ?=0° and?=90° were 165.05 N/mm and 114.47 N/mm.The test value of the shear strength were 132.39N/mm,122.73 N/mm,135.66 N/mm,199.13 N/mm,92.26 N/mm,172.76 N/mm,99.81 N/mm,89.52 N/mm,79.10 N/mm and 85.68 N/mm when ?=0°,?=90°,?=30°T,?=60°T,?=120°T,?=150°T,?=30°C,?=60°C,?=120°C and ?=150°C,respectively.The lateral resistance of teeth reached the maximum when the load were both parallel to the truss plate direction and the wood grain direction,and dropped to the minimum when the load were both perpendicular to the truss plate direction and the wood grain direction.The largest ultimate tension resistance under the three kinds of force forms was obtained in the shear-tension form,secondly in the pure shear form,and the lowest was obtained in the shear-compression form.(2)The results showed that the ultimate tensile strength of the steel plate is 377.12 N/mm~2,and the correction coefficient of steel plate is =0.98.And the design value of the lateral resistance of teeth in the four cases AA,AE,EA and EE,are 0.88 N/mm~2,0.63 N/mm~2,0.60N/mm~2,0.59 N/mm~2,respectively.The design value of tension resistance when ?=0° and?=90° were 92.43 N/mm and 64.10 N/mm.The design value of the shear strength of truss plate are 74.14 N/mm,68.73 N/mm,78.20 N/mm,111.51 N/mm,51.67 N/mm,96.75 N/mm,55.89N/mm,50.13 N/mm,44.30 N/mm,47.98 N/mm,when ?=0°??=90°??=30°T??=60°T??=120°T??=150°T??=30°C??=60°C??=120°C??=150°C.(3)The ultimate loads of the two types of light wood truss were between 20 and 25 kN,at the level of 12-15,with a certain degree of dispersion.The average ultimate loads of P and L type light wood truss were 22.45 kN and 22.94 kN,respectively,the coefficients of variation were 7.9% and 7.1%.It showed that the ultimate load of L type light wood truss was slightly higher than that of P type light wood truss,while the coefficient of variation was a little lower.Moreover,brittle failure occurred in the P type light wood truss during the loading stage or constant load stage when it reached the ultimate load.In addition,the stability of L type light wood truss is poor due to the smaller out of plane stiffness,which lateral deformation will occur after two times design load.(4)Based on the finite element method,the distribution of the stress,axial force and shear force of the parallel chord light wood truss were obtained.The results showed that the weakest link of the parallel chord light wood truss lies at the end of the joint and the place of concentrated load applied,which was consistent with the experimental results.The analysisresults showed that the finite element simulation software SAP 2000 could be used to predict the stress and deformation of light wood truss in practical application,and provide references for the design and application of light wood truss. |
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