Mechanical Model And Force Mechanism Analysis Of Mortise-tenon Joints Of Mountain Ancient Timber Structures

Our country is a mountainous country.Many ancient buildings are built on mountains.We call these ancient buildings which are built on mountains and closely combined with terrain as mountainous ancient buildings.The mechanical properties and structural characteristics of mountainous ancient buildings and plains ancient buildings are different because of the unequal height of their wooden columns.As a connecting member of ancient timber structure,mortise-tenon joint can resist horizontal load and reduce vibration by staggered friction and mutual extrusion between mortise and tenon,however,different wood and mortise size have great influence on its mechanical properties.At present,the research on mechanical properties of mountainous ancient buildings is lacking.The study on mortise-tenon joints fails to fully consider the effects of wood properties and the size of mortise-tenon joints on their mechanical properties.Based on this,two common mortise-tenon joint test models,straight mortise-tenon joint and dovetail mortise-tenon joint,are used as prototypes.A 3D solid model is built in ABAQUS finite element software to simulate the test process and verify the correctness of the finite element model..On this basis,the effects of wood properties and joint size on the mechanical properties of the mortise-tenon joints are simulated and calculated,and the M-? skeleton curves of the two joints were proposed.At the same time,this paper takes the test model of the column frame as the prototype,establishes the column frame model of a mountainous ancient building with unequal height column,and establishes the rob model in ABAQUS finite element software.Based on the M-? skeleton curve of mortise-tenon joints proposed in this paper,the spring element is used to simulate the mortise-tenon joint,and the horizontal load is simulated.By comparing P-? skeleton curves and bottom shear force of mountain unequal column frame and flat elevated column frame,the mechanical mechanism of mountainous ancient buildings is studied.The main conclusions are as follows:(1)The M-? skeleton curve of the straight mortise-tenon joint is a three-fold line of slip section,elastic section and yield section,and the M-? skeleton curve of the dovetail mortise-tenon joint is a two-fold line of elastic section and yield section.The M-? skeleton curve formula of the two joints fits well with the experimental data collected,which can reflect the mechanical behavior of mortise-tenon joints to a certain extent.(2)Two kinds of mortise-tenon joint column frame finite element models fit well with the test P-? skeleton curve,which proves that the application of M-? skeleton curve to column frame simulation is feasible.Comparing the P-? skeleton curves and bottom shear force of the mountain column frame and the flat column frame with two kinds of mortise-tenon joint,it can be seen that the mountain unequal column frame yields earlier when its displacement is consistent with the flat elevated column frame,and the shear force of the upper grounding column on the mountain column frame is about two times of the lower grounding column.It shows that the upper grounding column is the weak part of mountainous ancient buildings.(3)The existing ancient timber structures usually use straight mortise-tenon joints to connect the beams and columns.Dovetail mortise-tenon joints are mostly used to connect horizontal members such as eaves and foreheads and columns.This paper assumes that dovetail mortise-tenon joints are used to connect the beams and columns.By comparing the results of straight mortise-tenon joints with dovetail mortise-tenon joints,it is found that the bearing capacity of dovetail mortise-tenon joint is only about 1/2 of straight mortise-tenon joint,so it is reasonable to connect beam and column with straight mortise-tenon joints,and dovetail mortise-tenon joints to connect horizontal member and column.