Study on the Optimum design of Steel Washers for Timber.

在实际设计中，允许或工作的螺栓拔出阻力不是来自螺栓的拉伸阻力或允许伸长，而是主要来自允许在木材中嵌入钢垫圈。钢垫圈或边板的嵌入阻力对螺栓连接的极限抗力也有积极的影响。由于钢垫圈的嵌入刚度引起螺栓的二次轴力，从而增加了螺栓连接的极限抗力和延性。本文采用T.Kawai提出的分析模型--刚体-弹簧模型，分析了钢垫圈在木材中的荷载-埋入关系。在分析中，木材上的钢垫圈被视为地基上的板。假定该板由有限个刚性单元和支承在垂直于该板的外部弹簧上的有限个弹簧单元组成。该模型也可用于估算螺栓连接钢边板的弯曲变形。对于每种接缝结构，必须给出刚性块下木材的支承弹簧常数，因为支承刚度受木材边距和深度的影响。在此基础上，引入“有效基础宽度”的概念，引入“有效基础宽度”的概念，在考虑不同边际和深度的部分承载试验结果的基础上，分析了木材支承的钢制方垫圈及其埋入木材后的板弯变形。通过9种三种宽度、三种厚度组合的钢制方形垫圈的垫圈-木材轴承试验验证了分析结果，并对其进行了数值模拟分析。

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.