螺栓接头承受偏心载重时强度之分析与设计.doc

PAGE 10 PAGE 1 螺栓接頭承受偏心載重時強度之分析與設計 呂東苗 徐暐亭 李柏樺 中興大學土木工程系教授 中興大學土木工程 Abstract The ultimate analysis, which specified in AISC design manuals, has been used for the analysis of eccentrically loaded connections which are bolted. In the current AISC design manual (2005), tabulated solutions for eccentric loads inclined at specified angles (0°≦θ≦75°) from vertical are provided. For the cases which inclined angles are in the range of 75°≦θ≦360°, the current AISC manual does not furnish available tables to apply. Furthermore, the tabulated values are really obtained by assuming the eccentric load is applied at the same horizontal level as the c.g. of bolt or weld groups. However, the assumed position for applied loads is not a common practice and this could result in a misleading design, which is a possible highly overestimated design. This study conducts a comprehensive solution to overcome the problems as mentioned. Firstly, the methods to evaluate the strength of eccentrically loaded connections, which are not limited to the bolt or weld patterns listed in current AISC manuals, are presented and compared. A numerical procedure for the analysis of eccentric loads that are inclined at any angles (0°≦θ≦360°) from vertical is furnished. Secondly, written programs (in Fortran and Excel) were developed to perform the calculations. The programs are necessary to locate the instantaneous center of rotation, which is the main obstacle to the ultimate analysis. From the cases included in this study, it was found that the tabulated values using AISC design manuals could be as much as 116% higher than the ones using the ultimate analysis. Of course, this is not allowed in practice. This study points out the deficiencies of the current AISC design manual and presents an executable solution to deal with the problems that face the practicing engineers in their routine design. 1 前言 鋼結構樑柱構件接合方式以螺栓樑柱接頭最為常見，樑柱接頭會承受偏心載重(如圖1)，因此接頭會同時產生彎矩與剪力作用，