| In recent years,the development of modern wood structure in the construction industry has been widely concerned by the public with its advantages of renewable resources,low carbon environmental protection and good seismic performance.At present,the beam and column joints of wood frame are still mainly connected by bolts.A large number of studies have shown that bolt joints have some shortcomings,such as low initial stiffness,easy cracking of wood and limited seismic performance.How to effectively improve the bearing capacity and energy dissipation capacity of bolt joints of beam-column,give full play to the advantages of good seismic performance of wood structure,and provide more reference design ideas for practical engineering has become one of the urgent problems to be solved in wood structure buildings.Through experimental research,theoretical model prediction and finite element simulation,from the local node to the whole frame,this paper explores the mechanical properties of self-tapping screw joints,studies the mechanical properties of friction energy dissipation reinforced Knee brace joints,and establishes the theoretical prediction model of the hysteretic curve of friction energy dissipation Knee brace joints.Based on the results of joint test and theoretical model,the finite element model of the joint and frame reinforced by friction dissipation device is established,and the seismic performance of the joint and frame reinforced by friction dissipation device is analyzed.The main research contents and conclusions are as follows:(1)Monotonic and low-cycle reciprocating loading tests were carried out on oblique tapping screw joints to explore the mechanical properties of the self-tapping screw joints.The results show that self-tapping screws can not only effectively improve the elastic stiffness and bearing capacity of the joints,but also enhance the mechanical properties of wood to a certain extent,delaying the occurrence of brittle failure of wood splitting.In addition,from the perspective of stress mode,the bearing capacity of self-tapping screws in tension-shear mode is higher than that in compression-shear mode.At the same time,the mechanical properties of the tapping screw joints can also be used as the data basis of the theoretical prediction model,and can provide an important reference for the test of the Knee brace joints.(2)In this paper,a beam-column bolt joint is proposed,which is connected by tapping screws and strengthened by friction energy dissipation device.Two kinds of layout angles are set,and monotonic and low-cycle reciprocating loading is carried out on the friction energy dissipation joint,so as to explore the bending performance of the friction energy dissipation joint.The results show that the wood at the joint end of the Knee brace is not fractured and brittle when the Knee brace is connected by tapping screws,which indicates that the use of tapping screws can not only change the failure mode of the joint end,but also give full play to the function of the Knee brace by scientific research,thus strengthening the joint.At the same time,compared with ordinary nodes,the friction energy dissipation device strengthened different Angle of the joint can greatly improve the mechanical properties of the node,including the bearing capacity increased by 2.01 times,1.77 times,ductility coefficient increased by 179.86%,82.73%,energy dissipation capacity increased by 8.1 times,7.1 times.It shows that the joints strengthened by friction energy dissipation have significant improvement in bearing capacity,ductility and energy dissipation performance.(3)In this paper,a moment-angle theoretical curve prediction model of Knee brace reinforced by friction energy dissipation device is proposed.The model is based on the common beam-column bolt joint model,and obtained by superimposing self-tapping screw joint and friction energy dissipation Knee brace calculation model.By comparing with the experimental results of the joints,the theoretical curve prediction model of friction energy dissipation can effectively simulate the hysteretic properties of the joints and the pinching characteristics of the curves,indicating that the model has high accuracy and can provide valuable reference for practical engineering design and application.(4)In order to study the seismic performance of joints strengthened by friction energy dissipation in frame structures,finite element software Open Sees is used to establish a finite element analysis model from ordinary joints to joint joints and from ordinary frames to joint frames.The analysis results show that the finite element model of the common joint and the stile-supported joint has high accuracy in the fitting of the overall hysteretic characteristics of the joint,including the ultimate bearing capacity,pinching characteristics and energy dissipation capacity,which indicates that the finite element model of the joint can provide a reference for engineering design.In addition,the low-cycle reciprocating loading simulations were carried out for the trusses of single span and two trusses of two-span frames of ordinary frame and Knee brace,as well as the two-story two-span frames with different number of Knee brace.According to the simulation results,compared with the ordinary frame,the bearing capacity,elastic stiffness,ductility and energy dissipation capacity of the frame are significantly improved,while the elastic displacement of the frame is significantly decreased,which indicates that the friction energy dissipation of the frame can effectively improve the seismic performance of the frame.It is found that the seismic performance of the frame with different number of brackets is related to the number of brackets.The more friction dissipation of brackets,the greater the performance improvement of the frame. |
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