| The existing main structure of Guang-yue Tower in Liaocheng City,Shandong Province was built in the early years of Hongwu,Ming dynasty.The tower is composed of a brick stylobate,an open porch and a timber tower.The timber tower is four-eaved,with a gable-and-hip roof and horizontal cross ridges and eight sloping ridges(重檐四滴水歇山十字脊)on the stylobate.It has survived many earthquakes for six hundred years.However,there exist obvious tilting and torsional deformation in the main structure,and more serious deformation and damage have appeared in the major wood components.A structural safety assessment is needed.However,the main structure of Guang-yue Tower is complex,the structural system is not clear,and the mechanical performance of Tou-Kung joints is not clear.Based on the comprehensive investigation and the results of digital surveying and mapping of Guang-yue Tower,this paper carries out the experimental study of the mechanical properties of the Tou-Kung joints and finite element analysis to provide an important basis for the safety assessment of the main structure of Guang-yue Tower.In order to study the mechanical properties of Tou-Kung joints,this paper carried out static loading and quasi-static loading tests on the full-scale models of the Tou-Kung joint on the external column of the third floor of Guang-yue Tower.Under the vertical load,Tou-Kung joints transmits the load through the main aisle exposed tie beam,Kung,Qiao and Lu-Tou,its force mechanism is similar to the compression perpendicular to grain of wood.The failure mode of Tou-Kung joint is the local bearing failure of the middle Kua-Kung.The results of quasi-static tests show that the failure mode of the Tou-Kung joint is brittle failure of the Lu-Tou type.The hysteretic curves appeared to have a reverse S shape,and they were relatively full,indicating a significant energy consumption ability.The horizontal load applied to the Tou-Kung joint model was shared by Fang components,and the frictional force was applied between the flower arms and the main exposed tie beam,based on which the method for calculating the rigidity-displacement method was deduced based on the embedment deformation theory of wood,and the calculated result was found to correspond to the experimental data.For estimating the structural security of Guang-yue tower in Liaocheng City and in consideration of the construction features of Guang-yue tower such as the mortise and tenon joint,the brackets system and the special connection method of plinth and column,a finite element model is generated based on the digital survey of Guang-yue tower using Midas,the column-wall interaction and the construction features such as the mortise and tenon joint,the brackets system and the special connection method of plinth and column and so on are taken into consideration.By applying different load,static and sesmic response were analyzed,and the stress and strain distribution of Guang-yue tower under different load combination were calculated.The results indicated that the stress and the strain of Guang-yue tower is within the tolerance range,the present deformation of Guang-yue tower would result in some problems such as wall cracks,tenon pulled from mortise and component displacement,which are corresponded to the present situation.The analysis results would provide important support for the formulation of preventive protection programs. |
