Study On Seismic Behavior Of Straight Tenon Wood Joints Strengthened With Steel Plate With Locally Damaged Tenon

Wood structure architecture plays an important role in China’s architectural history.The ancients used all kinds of wood as raw materials and used mortise and tenon connection to create one architectural miracle after another.With its excellent seismic performance,many ancient wooden buildings have been preserved so far,but with the passage of time,various damage phenomena of ancient wooden buildings can not be ignored,among which fungal decay is one of the most common and harmful factors.Based on this,this paper artificially simulates the fungal decay damage at the tenon of the straight tenon,and designs a steel plate reinforcement scheme for the decay damage.Through the combination of quasi-static test and finite element simulation,the damage of tenon joints and the change of seismic performance after reinforcement are studied,so as to provide a basis for the protection and reinforcement of wooden structures of ancient buildings in China.The main contents are as follows:（1）In this paper,seven specimens of straight tenon joints are designed,which are nondestructive specimens,specimens with fungal decay damage rates of 5%,10%,and 15%respectively,and three specimens strengthened with steel plates on the basis of damage.Through the processing and analysis of the specimen data collected in the quasi-static test,the seismic performance changes of the straight tenon joints before and after damage and reinforcement are comprehensively evaluated by multiple indexes.（2）The deformation and failure phenomena of each specimen during the test show that the straight tenon joint has good deformation capacity,and there is no obvious failure phenomenon until the end of loading;Fungal decay damage reduces the deformation capacity of the straight tenon joint.During the loading process,the embedded pressure area of the specimen is more likely to produce local cracks,and the cracks are easier to develop along the hole,and the damage occurs when the rotation angle is small;The deformation capacity of the damaged joints after steel plate reinforcement is improved.When the fungal decay damage rate is 5%and 10%,the final rotation angle of the strengthened specimen can be restored to the nondestructive level,and no through cracks are observed after the test.（3）The skeleton curve shows that fungal decay damage has a great adverse effect on the bearing capacity of straight tenon joints under reciprocating load,and the bearing capacity of straight tenon joints decreases with the increase of damage rate;The bearing capacity of the specimens strengthened with steel plate is significanlly improved.The bearing capacity of the specimens with damage rate of 5%is basically repaired to the level without damage after reinforcement.Although the specimens with damage rate of 10%and 15%can not be repaited to the nondestructive level after reinforcement with steel plate,the bearing capacity has also been significantly strengthened.In addition,the stiffness degradation and strength attenuation of the straight tenon joints damaged by fungal decay are more significant than those without damage,and the energy dissipation capacity decreases significantly,while the energy dissipation capacity of the straight tenon joints strengthened with steel plate is significantly improved.（4）ABAQUS finite element software is used to simulate the damaged and strengthened straight tenon joints.Through the analysis and comparison of deformation,stress nephogram,hysteretic curve and skeleton curve,it shows that the simulation results can accurately reflect the stress distribution characteristics and the change of bearing capacity of each specimen.The model is reasonable and consistent with the phenomenon of quasi-static test.（5）Through the seismic performance indexes obtained in the quasi-static test,combined with the results of finite element simulation analysis,the seismic performance of the straight tenon joint is comprehensively evaluated.It can be seen that the fungal decay damage significantly reduces the seismic performance of the straight tenon joint;Strengthening the damaged joints with steel plates can effectively improve the seismic performance.The research results of this paper can provide a reference for the damage reinforcement scheme of tenon joints in ancient buildings.