| The properties of joint joints affect the overall stability of modern bamboo and wood structural members,and also affect the overall strength and stiffness of the structure.In the connection mode of modern bamboo and wood structures,bolted joints are indispensable,and the determination of the design bearing capacity of the joints of bamboo and wood components is also affected by the bearing strength of the pin grooves.In this paper,glued bamboo wood is used as the research material,and the material properties of the substrate and the yield strength of the pin shaft are tested;the influence of five influencing factors on the pressure bearing performance of the glued bamboo wood pin groove is analyzed,and the test values are compared with the six national standard pins.Based on the theoretical calculation value of groove bearing pressure,the calculation formula of pin groove bearing strength of different samples is proposed;the bearing performance of glued bamboo wood bolt connection joints and three influencing factors are thoroughly discussed,and the connection performance and main influencing factors of glued bamboo wood wood are clarified;based on Foschi formula,compared and analyzed the test value and simulation formula value,and compared the design value and test value of three kinds of national standard bolt joints,and proposed the calculation formula of the bearing capacity of glued bamboo and wood double shear bolt joints.The main research is as follows:(1)Measure the moisture content and density of each test piece and the compressive strength along the main direction of the grain,and use the three-point bending loading scheme to measure the yield strength of the steel pins and bolts.The material test results show that the specimens used in the test have uniform and stable mechanical properties,which meet the requirements of structural materials.(2)Under the premise of significance levelĪ±=0.05(the data has 95%confidence),the one-way analysis of variance method is used to obtain the following conclusions:with the increase of bolt diameter,the bearing strength of the pin groove of the specimen decreases.But the rate of decrease gradually decreases;the bearing capacity of the pin groove under the compression of the steel pin along the direction of the grain is significantly higher than that of the pin groove under the compression of the steel pin along the direction of the grain,and the yield load along the direction of the grain is higher than that of the yield load along the direction of the grain increased by 0.18 to 1.26 times;the pin groove under smooth contact conditions has higher load-carrying performance than the pin groove under thread contact conditions,and the bearing capacity of pin grooves under smooth conditions is 1.15 to 1.73 times higher than that under thread conditions;The compressive strength of the groove is BWB(bamboo-wood-bamboo)sample>WBW(wood-bamboo-wood)sample>GLT(glued wood)sample>CLT(cross-laminated wood)sample;The compressive strength decreases with the increase of immersion time,from the air-dried state to 3 days of immersion and from 3 days of immersion to 6 days of immersion,the decrease of the compressive strength is more obvious,and then decreases slightly with the extension of immersion time;The error between the measured value(5%d offset method and the half-hole pin-slot bearing method)and the calculated value(NDS theoretical formula)is within15%(except CLT),and the calculation formula for the pin-slot bearing strength of different samples is proposed.(3)Under the premise of significance levelĪ±=0.05(the data has 95%confidence),the following conclusions are obtained by the one-way analysis of variance:as the diameter of the bolt increases,the maximum load shows an increasing trend,and between 12 mm and 14 mm The growth rate of the maximum load in the diameter stage is larger than that in the diameter stage from 10 mm to 12 mm;as the bolt grade increases,the maximum load of the joint increases,and the bolt joint of class 8.8 shows a greater degree of bolt bending than the joint of class 10.9bolt;Different material types have different load-carrying capacity for bolted connections.In this test,BWB material has a higher load-bearing capacity than WBW material;Foschi formula is suitable for simulating the load-bearing performance of double-shear joints of glued bamboo and wood specimens(R~2>0.8).(4)The prediction results of Chinese GB standard,EU Eurocode 5 standard,American NDS standard and Johansen theoretical value on the bearing capacity of bolted connections of glued bamboo and wood structures show that in this test,Chinese GB standard,American NDS standard and Johansen theoretical value Glued bamboo and wood structures are relatively conservative.Based on the Eurocode 5 standard of the European Union,this study proposes a calculation formula for the bearing capacity of glued bamboo and wood double shear bolt joints.It has been verified that it has a stronger predictive ability. |
