Study on the Optimum design of Steel Washers for Timber.

点击翻译按钮获取中文摘要

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.