| Traditional Chinese architecture is a highlight in the history of world architecture,and wooden structure is the main structural form of traditional Chinese architecture.There are inevitably different degrees of damage inside the joints and wooden frames after a long service period.The precise study on mechanical analysis of the mortise-tenon joints and wooden frames is a prerequisite for the targeted and preventive protection of traditional wooden buildings.The most notable feature of traditional wooden building is that the mortise-tenon joints are commonly used for connection between beams and columns.The geometry of joints is different and there are usually gaps inside them.Therefore,the friction-slip-contact behavior of tenon and mortise makes the mechanical performance analysis of joints and frames more complicated.As a result,it is difficult to carry out scientific and reasonable protection measures for traditional architectures.Although there are many experimental analyses of mortise-tenon joints,they are limited by specific material properties,geometric properties and boundary conditions,the application of the results is often not universal.In this paper,the mechanical model of semi mortise-tenon joint in axial,shear and rotational degrees of freedom are deduced considering the gap and friction-slip-contact behavior of the joint,and the frictional behavior of the joint in the three degrees of freedom is analyzed.The mechanical models of penetrated mortise-tenon joint and lintel-mortise joint are also established for the need of the modeling requirements of typical wooden frames.The bending moment-rotation relationships of the proposed mechanical model of semi mortise-tenon joint,penetrated mortise-tenon joint and lintel-mortise joint are in good agreement with the results of the experimental and simulation models,indicating that the proposed mechanical model of such joints can be further applied to the mechanical behavior analysis of the whole wood frame.The mortise-tenon joint with frictional slip-contact behavior and the column foot joint with rotational behavior are simplified into virtual spring elements,then stiffness matrixes of the hybrid finite elements including mortise-tenon joint and column foot joint are derived respectively.Therefore,a single-span wooden frame with beam elements is established directly based the proposed hybrid finite elements.It is pointed out that the gaps inside the mortise-tenon joints in the wooden frame obviously weaken the lateral resistance of the wooden frame.The mechanical performance of the wooden frame with different size gaps is obviously different.Lateral performances of wooden frame are found to be associated closely with the contact states of mortise-tenon joint and column foot joint.In addition,the influences of geometrical dimensions of mortise-tenon joints and vertical load on the lateral resistance of wooden frames are revealed.The analysis approach of the nonlinear dynamical response of wooden frame is proposed,also the seismic performance of the wooden frame is evaluated based on the energy analysis of the dynamic system.The mechanism of the energy release and storage of the rocking wooden frame is revealed.The dynamic analysis shows that the input energy of the wooden frame is converted into kinetic energy,damping energy and work done by restoring force.The gravitational potential energy of the roof is the main part of the work done by restoring force.The seismic input energy is mainly converted into the gravitational potential energy of the roof and the kinetic energy of the wooden frame.During the rocking process of the wooden frame,the kinetic energy and the gravitational potential energy are converted back and forth,and the input energy is finally converted into irreversible damping energy and friction energy dissipation.The column-and-tie wooden frame with beam elements is established based on the mechanical models of mortise-tenon joints and column foot of traditional wooden structures.The pseudo-static analysis of the column-and-tie wooden frame is conducted for study on the mechanical performance of it under the influence of the uniform and nonuniform gaps inside the mortise-tenon joints.Also,the energy dissipation characteristics of the column-and-tie wooden frame under the action of earthquake are analyzed.According to the static and dynamic analysis of the most unfavorable and most favorable working conditions determined by the bearing capacity,the gaps not only cause the loss of the restoring force of the tenon-and-mortise joints,but also cause the loss of frictional energy dissipation of the mortise-tenon joints of the wooden frame.Furthermore,the post-and-lintel wooden frame with beam elements is also established based on the mechanical models of mortise-tenon joints and column foot.The pseudo-static analysis of the column-and-tie wooden frame is conducted for study on the mechanical performance of it under the influence of the uniform and non-uniform gaps inside the mortise-tenon joints.Also,the energy dissipation characteristics of the columnand-tie wooden frame under the action of earthquake are analyzed.Finally,the lateral force performance and dynamic energy dissipation characteristics of the column-and-tie wooden frame and the post-and-lintel wooden frame are analyzed contrastively.The results show that the lateral stiffness of the post-and-lintel wooden frame is greater than that of the column-and-tie wooden frame;the energy storage capacity of the gravitational potential energy of the column-and-tie wooden frame is stronger than that of the postand-lintel wooden frame,and the capacity of dissipated energy from friction of the tenonmortise joint is weaker than that of the column-and-tie wooden frame. |
