Mortise-tenon Joints Of Strengthened Wood Structure With Viscoelastic Damper Experiment Study

One of the biggest advantages of wood structure is that it has good seismic performance,and the semi-rigid connection of mortise-tenon joints plays a great role in the seismic performance of wood structure.In the previous study,we found that the resistance moment of mortise-tenon joints is mainly divided into embed and friction,but the damage of tenon width in reality will weaken the seismic performance of mortise-tenon joints,so it is necessary to strengthen so me joints.As a result,the number and type of special dampers for wooden structures are much less than those for reinforced concrete structures.Based on the above problems,a fan viscoelastic damper was used to carry out low-cycle repeated loading tests on the joints with half tenon and dovetail tenon,and the results were compared with those on the joints without dampers.The main contents and conclusions are as follows:(1)In Chapter 2,the physical and mechanical properties of two kinds of wood,pine and Chinese fir,were tested,and the physical and mechanical performance indexes of the two kinds of wood were obtained.It was found that the other indexes were higher than that of Chinese fir except for the smaller moisture content.(2)In Chapter 3,a total of 12 specimens of half tenon and dovetail tenon with different wood species and different damage degree were made,and the low-cycle repeated loading tests were carried out.According to the analysis of test results,it is found that the hysteretic cu rves of 12 joints are all anti-Z shape and obvious pinch,and the tendency of tenon pull-out curve is basically the same.But the hysteretic loop of pine specimens is fuller while its stiffness,bearing capacity and energy-dissipation capacity are larger t han that of the Chinese fir specimens under the same loading.The hysteretic curve area,initial stiffness and energy-dissipation capacity of the intact joints are larger than those of the damaged joints.However,the deformation ability of damaged joints and the pinch effect of hysteretic curve are larger than that of intact joints,and the limit angle of damaged No.2 joint specimen is larger than that of intact joints.There are two main forms of joint failure: tenon and tenon buckling.(3)In Chapter 4,a total of 12 specimens of half tenon and dovetail tenon with intact and damaged joints were made,and repeated low-cycle loading tests were carried out.According to the analysis of the test results,the hysteretic curves of the 12 joints after reinforcement were still in the shape of inverse Z,positively and negatively asymmetrical,the pinch effect is obvious,and the tendency of the tonon pull-out curve is the same.However,after strengthened,the hysteretic curve area,negative stiffness and energy-dissipation capacity of the joints increased significantly,especially the maximum moment bearing capacity increased by 2 times or more.After strengthening,the deformation capacity of intact joints was improved,and the pinch effect of hysteretic curve was smaller.There are three types of joint failure: bolt pull-out,nut shedding,and tenon pull-out.(4)In Chapter 5,through overall comparison of the experimental results of the above 24 joints,it found that the dampers greatly improved the stiffness and energy-dissipation capacity of the 12 joints after strengthened,but there were also some defects on the instable fixation and the structural limitation by the installation technology.Therefore,some suggestions for improving the damper were put forward.