榫卯间缝隙对古建筑木结构燕尾榫节点承载性能影响的有限元分析

The influence of gap between tenon and mortise on the bearing behavior of the dovetail joints in ancient timber structure by finite element analysis

以宋《营造法式》为标尺,建立分析2个一榀燕尾榫柱架有限元模型,包括节点无缝隙柱架模型和节点有缝隙柱架模型。在不同竖向荷载下,对2种模型进行水平往复加载模拟,得出2种模型的滞回曲线及骨架曲线,以分析屋顶质量和榫卯间缝隙对木结构节点承载性能的影响。结果表明:木结构的屋顶质量越大,结构整体刚度越大,耗能越可观;2种柱架的榫头与卯口之间存在较明显的挤压变形,滞回曲线都呈现"捏缩"现象,但节点有缝隙模型由于榫卯节点之间的缝隙导致节点紧密度下降,其滞回环饱满度差,结构耗能能力弱,抗震性能差。通过对比分析节点无缝隙和有缝隙模型的计算模拟结果,得出燕尾榫榫卯节点的破坏方式和缝隙对燕尾榫柱架造成耗能减少、刚度降低的影响,为古建筑抗震性能研究和榫卯节点处修缮加固提供借鉴。

According to Ying-zao-fa-shi of Song Dynasty,two dovetail joints frame models were developed and analyzed,including two joints with gap and without the gap.The typical dovetail joints frame model of ancient timber structure was subject to the horizontal reciprocating load under different vertical load.The hysteresis curve and skeleton curve were obtained to analyze the influence of roof mass and the gap between tenon and mortise on the bearing behavior of the joint in wooden structure.It can be concluded that to some extent,the heavier the roof and the bigger the overall structure stiffness,the more energy is dissipated.Compressional deformation was observed in mortise and tenon joint.‘Pinching'phenomenon can be observed based on the hysteresis curves.However,the gap between tenon and mortise led to the decreasing of the joint tightness and worse hysteresis loop plumpness of the seam joint model.It also led to lower energy dissipation capacity and worse seismic performance in the structure.The failure mode of the dovetail tenon and mortise joint,the influence of the less dissipated energy and the lower stiffness caused by the gap between tenon and mortise were obtained by analyzing the numerical simulation results,which provide a theoretical basis for the study on the seismic performance of ancient wooden structures,the reinforcement and remedy for tenon and mortise.