| Connection is the key to the design of wood and bamboo structure.The wood-steel-wood connection is easy to install,reliable for force transmission,and has little influence on the appearance of the material.Thus,it is widely used in the connection of wood and bamboo structures.Laminated veneer bamboo is a new type of engineering bamboo material,which is made by glueing and pressing bamboo slivers together.The ratio of strength to weight of laminated veneer bamboo is relatively large among all the engineering materials.This paper focus on the load-carrying performance of the bolted bamboo-steel-bamboo connection.The basic physical and mechanical properties of the laminated veneer bamboo as well as the bending yield moment of the bolts were measured.Also,experiments were taken to analyze the dowel-bending strength and the performance of the bolted connection.Finally,the design method and structural requirements of the connetion were summarized.The main results are as follows:(1)The physical and mechanical properties of the bonded bamboo material were determined,and its lightweight,high-strength properties were pointed out.(2)The dowel-bending strength of laminated veneer bamboo was measured.There were only one failure mode for load parallel to grain and two failure modes for load perpendicular to grain.The size of the specimen(height,width and thickness),diameter of bolt and load direction all had influence on the results so that the standards for specimen were proposed.The theoretical calculation method for wood was not suitable for laminated veneer bamboo so the calculation formula was deduced based on the results of experiments.(3)The load-carrying performance of single bolted joints was experimented.The yield mechanism and the ultimate failure mode were analyzed and the influence caused by bearing direction,diameter and end of bolt,thickness of member were discussed.The result showed that the thickness-diameter ratio was an important factor in determining the yield mode of bolt.When the ratio is relatively large,the bolts tend to yield with two plastic hinges.Thus,the thickness of the member is not supposed to be less than 8 times the diameter of bolt.Also,the end distance is not supposed to be less than 6 times of the bolt diameter and the margin is not supposed to be less than 3 times of it.In addition,the load-displacement curve was simulated using the Foschi model and the result turned out to be good.Finally,the calculation formula for the load-carrying capability of single bolted joint was deduced.(4)The load-carrying performance of multiple bolted joints was experimented.The yield mode of each bolt performed just in the same way as that in single bolt joint.Effects caused by the number of bolt rows,row space and bolt numbers were analyzed.It is recommended that space between bolts be not less than 5 times the diameter of bolt in the parallel-to-grain direction and 3 times of that in the perpendicular-to-grain direction.The Foschi model was used to simulate the load-displacement curves and it was found that the simulation results had some error and the reasons were discussed.Also,the effective bolt number was analyzed and the result showed that when the distance between the bolts in the parallel-to-grain direction reached 9 times the diameter of bolt,the effective number of bolt equaled to actual number of bolts.Finally,the calculation formula for the load-carrying capability of multiple bolted joints was deduced.(5)The numerical simulation was carried out by ABAQUS and the results turned out to be good.Stress distribution of the bolt hole and the influence caused by bolt spacing was analyzed. |
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