Study on the Optimum design of Steel Washers for Timber.

在实际设计中，螺栓的允许拔出阻力或工作拔出阻力并不来自螺栓的抗拉阻力或允许伸长，而主要来自钢垫圈在木材中的允许嵌入量。钢垫圈或侧板的嵌入阻力对螺栓连接的极限侧向阻力也有积极的影响。本文采用T. Kawai提出的“刚性体-弹簧模型”，分析了钢垫圈在木材中的荷载-嵌入关系，并对钢垫圈在木材中的嵌入量进行了分析。在分析中，将木材上的钢垫圈视为基础上的板。假设板由有限刚性单元和有限弹簧单元组成，有限弹簧单元由垂直于板的外部弹簧支撑。该模型也可应用于螺栓连接钢侧板弯曲变形的估算。由于木材的边缘和深度会影响木材的承载刚度，因此必须给出每种节点配置下刚性块体下木材的承载弹簧常数。在此基础上，引入“有效基础宽度”的概念，计算了考虑不同裕度和深度的局部承载力试验结果的承载力常数，并利用基于“有效基础宽度”计算的承载力弹簧常数，分析了木支承和嵌入木中的钢制方垫圈的板弯曲变形。通过3种宽度、3种厚度的9种组合方垫圈的垫圈-木材承载试验，验证了分析结果，并通过数值模拟得到了一些认识。

In practical design, allowable or working bolt-withdrawal resistance does not come from tensile resistance or allowable elongation of bolts but mostly comes from allowable embedment of steel washers into timber. Embedding resistance of steel washers or side plates also has a positive effect on the ultimate lateral resistance of bolted joints. It is because their embedding stiffness causes the secondary axial forces of the bolts that increase the ultimate lateral resistance and ductility of the bolted joints.In this study, load-embedment relationships of steel washers into timber are analyzed applying the "Rigid Bodies-Springs Model", which is an analytical model proposed by T.Kawai. In the analyses, a steel washer on timber is regarded as a plate on a foundation. This plate is assumed to consist of finite rigid elements connected with finite spring elements supported on external springs normal to the plate. This modeling can also be applied to estimate the plate-bending deformation of steel side plates of bolted joints. Bearing spring constants of timber under rigid blocks must be given for each joint configuration because the bearing stiffness are affected by margins and depths of timber. Then, the bearing constants are calculated introducing a concept of "effective foundation width" derived from the previous results of partial bearing tests considering various margins and depths.Plate-bending deformation of steel square washers supported on timber and their embedment into timber are analyzed using the bearing spring constants calculated based on the "effective foundation width". The analyzed results are verified with washer-timber bearing tests with steel square washers of nine combinations of three kinds of width and three kinds of thickness.Then some knowledges were obtained by simulation based on numerical analysis.