Research On Mechanical Properties Of Ethnic Wood Structures In Southeast Guizhou

The Southeast Miao and Dong Autonomous Prefecture of Guizhou Province is an autonomous prefecture for ethnic minorities.There are various forms of ethnic wooden structures,including drum towers,wind and rain Bridges,and crossing style dwellings,which are the important carriers of ethnic culture and humanistic spirit.These wooden structures have been damaged by human and natural erosion for a long time,such as timber groove decay,tenon and mortise joint loosening and frame tilting etc.In order to repair and reinforce the national timber structures,the anti-overturning ability and the stress mechanism of the joints must be analyzed and evaluated.There are various types of traditional wooden tenon and mortise joints and various frame forms.Through the analysis of relevant literature,the existing studies on wooden structure joints and wooden frames mostly refer to the architectural design of Han nationality palace and tower,while the research on the wooden frame of moron and mortise joints with throughpin adopted in southeast Guizhou is relatively vacant.Supported by the major research project of innovative groups of Guizhou Education Department "Research and Innovation Team of Southeast Ethnic Architecture"(KY [2017]048)and the science and technology plan project of Guizhou Province "Research Center of Construction Techniques and Industrialization of Southeast Ethnic Architecture"(No.7169 of Southeast Ethnic Architecture "LH [2017]),The full-scale mechanical tests on mortise and tenon joints and wooden frames of wooden structures in Southeast of Guizhou Province have been carried out in this thesis,and the finite element analysis software is utilized to deeply explore the mechanical characteristics and failure forms of ethnic wooden structures in Southeast of Guizhou Province.The main contents of the research are as follows:(1)Experimental study and finite element numerical simulation analysis of the bending performance for tenon joints with through pinDesign for two full size tenon joints with through pin(round pin)under monotonic loading experiment,through the analysis of test data for the moment-rotation curve,amount of pulling tenon-rotation curve of the joints,combined with the experimental phenomenon analysis joints under monotonic static load deformation characteristics,working principle and failure form.The results show that the failure of the joint is mainly due to the deformation of the tenon along the grain and the tear of the cross grain under the pressure.The columns and beams themselves are in good condition.The tenon joints with through pin show better antipulling tenon performance.The finite element software ABAQUS was used to simulate the through pin(round pin)joint and compared with the experimental results.It was found that the overall variation trend of M-θ curve was basically the same between the numerical simulation and the test,and the error was within the allowable range,which met the requirements of engineering precision.On this basis,the pin structure,the parameters of friction coefficient,section height and section width of the tenon were selected for parameterization analysis.The main conclusions are as follows: The flexural bearing capacity of the tenon joints with through pin(round pin and square pin)mainly depends on the compressive capacity of the transverse grain of the transverse beam,the tenon joints with through pin(square pin)show better ductile deformation ability;when the friction coefficient μ is in the range of 0.2～0.5,the yield moment of the joint can be significantly increased with the increase of friction coefficient,but the increase of maximum moment of the joint is relatively small;When the height H of the tenon is in the range of 110mm～190mm,the initial rotational stiffness and the maximum moment of the joint are improved to varying degrees with the increase of the tenon height,and the deformation of the bending moment-rotational angle curve gradually slow down from the elastic stage to the plastic stage.When the tenon width B is within the range of40mm～80mm,the yield moment and the maximum moment of the joint are significantly improved with the increase of the tenon width.(2)Experimental study and finite element numerical simulation analysis of mechanical properties of a single column-and-tie wooden frameThe horizontal static monotonic loading test was carried out to design one piece of fullsize column-and-tie wooden frame,and the horizontal load-displacement curve and tenon pulling curve were obtained.The bearing capacity,deformation characteristics and overall failure modes of the wooden frame were analyzed.The test results show that the sockets at the lower side of the central column have a large deviation,which makes it easy to take off the tenon.The failure of the tenon joint with inner through pin is mainly manifested as the extrusion depression of the tenon and the sockets.These two kinds of joints are the key joints of the wooden frame.The finite element software ABAQUS was used to carry out the numerical simulation of one piece of full-size column-and-tie wooden frame and compared with the experimental results.It was found that the simulation results were basically consistent with the experimental results.On this basis,the internal stress variation characteristics of the wooden frame are analyzed in detail.It is found that the anti-overturning ability of the wooden frame mainly depends on the compressive strength of the connecting beam stripes.On the basis of the previous research,the numerical simulation of the wooden frame under horizontal reciprocating loads is carried out.It can be seen that the hysteretic curves of the frame under different column top loads are all Z-shaped and have obvious "pinching" effect,and the hysteretic curves are relatively full,showing good energy dissipation capacity.The stiffness of the frame under different column top loads is approximately linear degradation,and the degradation rate is consistent,with the increase of the column top load,the degradation rate of the frame stiffness will not accelerate.This study provides a theoretical basis for the evaluation of the performance of wooden structure of Southeast of Guizhou Province ethnic group,and provides a theoretical basis and technical parameters for its maintenance and post-disaster maintenance of wood structure of Southeast of Guizhou Province ethnic group,which has important theoretical significance and engineering practical value.