Study On Seismic Performance Of Loose Dovetail Tenon And Reinforced Joints Of Wooden Structure Of Ancient Buildings

Chinese ancient building wooden structure has excellent seismic performance,dovetail mortise head is a special structure with wide outside and narrow inside,and the corresponding mouth is large and small outside,which can limit the free displacement along the mortise width and mortise depth.However,due to the influence of natural factors and the drying and aging of wood,the dovetail joints of ancient building wooden structures are prone to loosening.Excessive loosening is easy to cause mortise to be pulled out under the action of earthquake,which has become an important factor affecting structural safety.It is of great significance to obtain the seismic performance of dovetail joints under different degrees of loosening and after taking reinforcement measures for the seismic assessment and repair and reinforcement of wooden structures of ancient buildings.Taking the dovetail mortise of wood structure as the research object,through joint model test and finite element analysis,the force mechanism and seismic performance of loose dovetail joints of wood structure were studied,and the changes of performance indicators such as intact joints,different degrees of loose joints and reinforced joints,bending moment-angle curve and stiffness degradation were obtained.The influence of loosening on the seismic performance of the structure is revealed,and the correspondence between looseness,seismic intensity and joint failure mode is constructed,which provides basic data reference for the establishment of nodal seismic reinforcement method.The main research work carried out is as follows:(1)Study the force transmission mechanism,force mechanism and failure mode of loose dovetail joints of wooden structures of ancient buildings,form a loose joint reinforcement method and its structural measures,and apply the joint reinforcement method to the experimental joint and finite element model.(2)Make 12 dovetail tenon joint full-scale models with general pat fang,simulate loosening by reducing the size of their mortise,and obtain the hysteresis curve,skeleton curve and energy dissipation curve of the joint by quasi-static test,and analyze its failure mode,bearing capacity,stiffness degradation and energy dissipation capacity.(3)Study the change law of seismic performance indicators of each joint with the increase of loosening under different loosening degrees;The unreinforced joints and the joints with GFRP and section steel non-destructive reinforcement were tested and studied,and the changes of various seismic performance indicators of dovetail joints under unreinforced and reinforced measures were compared and analyzed.The similarities and differences in the seismic performance of damaged joints and intact joints of ancient buildings were revealed,and the joints with different degrees of damage were tested and studied after non-destructive reinforcement of section steel,and the seismic performance indicators of intact joints and section steel non-destructive reinforcement and intact joints were compared and analyzed.(4)Numerical simulation was carried out on dovetail joints,section steel non-destructive reinforcement joints and damage reinforcement joints with different degrees of looseness,and the stress distribution law and deformation of key parts of the joint were analyzed,and the test results were compared with the test results to verify the rationality of numerical analysis.On this basis,the parameters such as friction coefficient,material properties,axial load and different sizes of vertical support of section steel reinforcement components are changed to study their influence on the joint force performance.