| Dong drum tower,as a traditional wooden structure building of ethnic minorities with distinctive regional characteristics in China,plays an important role in the cultural and tourism development of Qiandongnan Prefecture.There are not only a large number of completed wooden drum towers in the area,but also new ones are still being built due to socio-economic development and cultural tourism needs.The drum towers are usually built by experienced local palm ink masters.Due to the lack of scientific analysis and calculation,and without professional seismic design and safety assessment,they are prone to damage under the action of larger intensity earthquakes.Therefore,the research on the seismic performance of the wooden drum tower buildings in Qian southeast China is of great significance to protect the ethnic cultural diversity of China and give life to drum tower buildings.Based on this,this paper,with the support of the National Natural Science Foundation of China(52068009),firstly takes the pin-through tenon joint of wooden drum tower in Qian southeast China as the research object,designs and produces three groups of tenon joint specimens with open-pin,concealed-pin and non-pin,conducts the quasi-static test on them respectively,and carries out detailed analysis on the working mechanism,damage morphology,hysteresis characteristics and other properties of various nodes.On this basis,a refined numerical model of the open-pin tenon joint was established using ABAQUS software,and the effects of changes in parameters such as tenon height,tenon thickness,post diameter and friction coefficient on the mechanical properties of the node were investigated by numerical analysis.Combined with the semi-rigid characteristics of the tenon joint in Chapter 2,a finite element analysis model of the spatial rod system of the drum tower was established using ABAQUS software with the Kaihuai Drum Tower in Kaili as the research object,and the mechanical properties of the drum tower structure under normal use and multiple and rare earthquakes were analyzed.The main conclusions are as follows:(1)The damage characteristics,hysteresis characteristics,load carrying performance,stiffness variation characteristics and energy dissipation characteristics of different through-pin tenon joints were studied by the quasi-static tests.The results of the study show that the main damage of the three types of tenon joints under repeated low circumferential loading is in the form of smooth grain pulling of the wood at the variable section and extending to the end of the tenon,where the concealed-pin is located at the variable section of the tenon,leading to the weakening of its cross-sectional integrity,and its damage is in the form of shear damage of the small tenon at the later stage of loading,and the pins inhibit the tenon detachment of the node to a certain extent.The hysteresis curves of all three types of tenon joint specimens showed inverse Z-shape,with obvious pinching effect,and large frictional slip and extrusion deformation between tenon and mortise during loading,and the load capacity,energy dissipation capacity and stiffness of open-pin tenon joint were significantly higher than those of concealed-pin and non-pin tenon joints.(2)The damage characteristics,hysteresis curves and skeleton curves of the finite element model of the open-pin tenon joint are approximately the same as those of the experimental model,which verifies the reliability of the finite element modeling.The results of parametric analysis show that: the influence of column diameter and tenon thickness on the node bearing capacity is significant,the node bearing capacity increases with the increase of column diameter and friction coefficient,while the tenon height and friction coefficient have less influence on the node bearing capacity,the node bearing capacity will increase to some extent with the increase of tenon height and friction coefficient.(3)ABAQUS software was used to establish a finite element analysis model of the space bar system of the drum tower,and the force deformation characteristics of the structure under normal use were analyzed.The results of the study show that the maximum vertical displacement of the drum tower under self-weight occurs on the2 nd floor beam,and because the beam connected to it cantilevers out partly,the upper load is transmitted to the melon column above the beam,resulting in a substantial increase in its deformation.The bending moment of the ground floor members of the drum tower is mainly concentrated in the mortise and tenon joint and the span position of the beam,while for the ground floor through the square,the bending moment is relatively small compared to that of the beam and only plays a connecting role.Some improvement measures are provided for the corresponding weak parts.(4)On the basis of the above,the modal and dynamic time-history analysis of the finite element model of the drum tower was carried out.The research results show that the 1st and 2nd order frequencies of the drum tower are 0.325 Hz and 0.328 Hz,and the vibration direction is two horizontal planar motions.The form of rigid connection of column legs has a significant effect on the model frequency of the drum tower.The connection method of wooden columns placed on the foundation stones ensures the flexibility of the structure as well as the long-period characteristics,which is conducive to the better absorption of seismic energy of the structure in the process of seismic resistance.Under the excitation of Takochi-oki wave with peak acceleration of 125 gal and Lanzhou artificial wave,the maximum interlayer displacement angle of the structure is greater than the limit value of 0.02 rad specified in GB/T51226-2017 "Technical Standards for Multi-story and Higt rise Timber Buildings",but the synergy of key points of the structure is good,and no damage occurs.It shows that the drum tower still has good deformation and collapse resistance under rare earthquakes.The stress distribution of the structure under Takochi-oki wave excitation with a peak acceleration of 125 gal was analyzed,and corresponding improvement measures were provided for the seismically weak parts of the drum tower. |
