古建筑木结构燕尾榫节点抗震性能及尺寸效应试验研究

为研究燕尾榫节点的抗震性能，考虑竖向荷载、普柏枋、雀替及尺寸效应的影响，对7个按宋《营造法式》制作的燕尾榫节点模型进行了水平低周反复荷载试验，对比分析节点的破坏形态、滞回特性、转动弯矩、转动刚度和耗能等抗震性能及其随各影响因素的变化规律。结果表明：燕尾榫节点破坏主要表现为榫头部分拔出，榫头与卯口间产生明显挤压变形，枋、柱整体完好；未施加竖向荷载的节点出现榫头沿柱纵向滑移现象；带普柏枋节点榫头拔出量较小，在普柏枋与馒头榫连接边缘发生局部剪切变形；带雀替节点在转角较大时，通过暗销连接的枋与雀替逐渐分离。节点弯矩 转角滞回曲线以反“Z”形为主，有明显的“捏缩”效应；竖向荷载越大，滞回曲线越饱满；带普柏枋燕尾榫节点的滞回曲线更平滑，对称性较好；带雀替燕尾榫节点的滞回曲线左右明显不对称。燕尾榫节点的正向转动弯矩随竖向荷载的增大而逐渐降低，而反向转动弯矩逐渐提高；普柏枋显著提高了节点的正反向转动弯矩，而雀替仅提高节点的正向转动弯矩。带普柏枋节点的转动刚度较大，而耗能能力较弱；雀替在与枋脱离前可以有效提高节点的耗能能力。不同尺寸燕尾榫节点的转动弯矩与转动刚度不满足模型相似关系，拟合的尺寸影响关系可为实际工程提供理论参考。

Experimental study on seismic behavior and size effect of dovetail mortise-tenon joints of ancient timber buildings

In order to investigate the seismic performance of the mortise-tenon joints, considering the influences of vertical load, Pubofang, sparrowbrace and size effect, the low-cycle reversed loading tests were carried out. Seven mortise-tenon joints were made as the fabrications methods of Song Dynasty. The seismic behavior and their change laws, such as failure patterns, hysteretic behavior, bearing capacity, degeneration of stiffness and energy dissipation, were compared and analyzed. The results show that the failure patterns are mainly partial evulsion of tenon and extrusion deformation of mortise and tenon, and the beams and columns are intact. The tenon slips longitudinally along the length of the column without vertical load; under the influence of Pubofang, the evulsion of the tenon is smaller and shear deformation occurs on the edge of the connection between Pubofang and Mantou mortise. As the rotation rises, the sparrow brace separates from the beam gradually. The hysteretic loops are Z type, and have obvious gathering effect. The hysteretic loops become fuller when the vertical load increases. The hysteretic loops of the joint with Pubofang is smoother and the symmetry is better, while the loops with sparrow brace shows evident asymmetry. With the increase of the vertical load, the opposite bearing capacity is higher, but the forward bearing capacity is lower. Pubofang increases the bearing capacity dramatically in both directions, while the sparrow brace only works in the forward. The rigidity of the joint with Pubofang improves greatly, but the energy dissipating capacity becomes weaker. The sparrow brace improves the energy dissipating capacity just in the primary stage. The bearing capacity and rigidity of the joints are all against the similarity relationship, and the theory basis could be provided according to the fitted formulas.