Experimental Study On Seismic Performance And Seismic Fragility Analysis Of Column-and-tie Timber Structure

As one of the main forms of Chinese traditional residential buildings,the column-and-tie timber structure is still widely used in southern China with its flexible and light structural system.However,there are few relevant codes and standards about the seismic measures of the column-and-tie timber structure,which largely depends on the experience of craftsmen to a large extent,resulting in great potential safety hazards.At present,the research on the mechanical properties of the column-and-tie timber structure is insufficient in the domestic and overseas.Therefore,it is necessary to study the seismic mechanism and weak links of the column-and-tie timber structure,so as to scientifically evaluate its seismic performance.The major research contents and results of this paper are as follows:(1)Taking the typical mortise-tenon joints in traditional column-and-tie timber houses in western Sichuan as the research object,the continuous tenon joint and hooked tenon joint were designed and manufactured according to the scale of 1:1.33.Through low-cycle reversed loading test on the Fang end,the failure process and failure mode of the joints were observed,and the moment-rotation curves of the joints were obtained.The test results show that both the continuous tenon joint and hooked tenon joint have strong deformation ability.During the whole loading process,the deformation and damage of the specimens mainly occur in the core area of mortise-tenon joint,while the column and Fang are basically intact.The moment-rotation hysteresis curves of all joints are anti-Z shape,and there are different degrees of "pinch" effect near the equilibrium position,with obvious slip.(2)The nonlinear numerical simulation analysis of typical mortise-tenon joints in column-and-tie timber structure was carried out by using ABAQUS finite element software,and the calculated results were in good agreement with the experimental results.Besides,the contact state and stress distribution of mortise and tenon were obtained.On this basis,the ABAQUS model was established to analyze the influence of friction coefficient,looseness and wood property on the mechanical properties of the joints,and the influence rules of various parameters were obtained.(3)Based on the test and simulation results,the force mechanism of typical mortise-tenon joint was analyzed.On the basis of some simplified assumptions,the moment-rotation relationship of the joints was deduced according to the physical relationship,mechanical balance and deformation compatibility conditions.The theoretical results are in good agreement with the experimental results.(4)A 1:2 scaled column-and-tie timber structure with two-layer and two-span was designed and made,and the seismic waves equivalent to frequently occurred 7-degree,fortification 7-degree,rarely occurred 7-degree were input in turn.The failure modes of the whole structure and the details during the test were observed,and the dynamic responses of the model structure,such as acceleration,displacement,seismic shear and strain,were studied.Meanwhile,the dynamic characteristics of the model,such as natural frequency and damping ratio,were obtained through white noise.Test results show that the model structure still does not collapse under the rarely occurred 7-degree,and the maximum inter-story drift angle is 1/53,which demonstrates that this kind of structure has good deformation capacity and anti-collapse ability.(5)The modal analysis and dynamic elasto-plastic analysis of the column-and-tie timber structure were carried out by ANSYS finite element software.The dynamic characteristics,acceleration response,displacement response,maximum shear distribution and hysteresis curve obtained by simulation were compared with the test results.On the basis of validating the correctness of the simulation,combined with the seismic codes of China,seismic data and the research results of relevant scholars,the performance level of wood structures is divided into five grades: basically intact,slightly damaged,moderately damaged,severely damaged and collapsed,and its performance level is quantified.The peak acceleration is used as the intensity index of ground motion,and the maximum inter-story drift angle is used as the structural response index.22 seismic waves were selected to analyze the seismic vulnerability of colum-and-tie timber structures.Finally,the probabilities of different failure states of typical colum-and-tie timber structure were obtained under frequently occurred7-degree,fortification 7-degree,rarely occurred 7-degree.