A STUDY ON THE DEVELOPMENT OF STABILITY DESIGN METHODS FOR STEEL FRAMES

本研究的目的是建立钢框架的稳定设计方法。首先，对钢框架的稳定设计方法进行了综述。其次，提出了一种新的框架稳定性设计方法。与有效屈曲长度的概念不同，该方法是基于弹性二阶分析的。在这种方法中，引入与缺陷相对应的等效初始挠度是至关重要的。为此，提出了一种新的基于曲率的等效挠度计算公式。此外，还提出了一种方法来解释该公式在阶梯形截面框架中的系统应用。通过算例验证了该方法的有效性。最后，给出了考虑构件板局部屈曲的二阶分析的钢框架强度简化分析。在分析中，引入了短柱的初始等效挠度和局部屈曲准则。另一方面，虽然已经进行了几个详细的分析来明确互动行为，但彼此之间几乎没有达成一致的意见。结果表明，采用力矩-推力-曲率关系的分析方法与Q因子法的分析结果吻合较好，实验证实了Q因子法的准确性。通过与基于力矩-推力-曲率关系的简化分析进行比较，验证了简化分析的有效性。

The purpose of this study is to develop a design method for stability of steel frames. At the beginning, a critical review of stability design methods for steel frames is performed. Next, a new stability design method for frames is presented. Contray to the effective buckling length concept, the proposed method is based on the elastic second-order analysis. In this method, the introduction of equivalent initial deflections corresponding to the imperfections is of utmost importance. Therefore, a new equivalent deflection formula using curvature is suggested. Moreover, a methodology is proposed to explain the systematic application of this formula to a frame with stepped cross section. The validity of the method is demonstrated by some examples. Finally, a simplified analysis of steel frame strength by the second-order analysis, consideringthe local buckling of component plates, is shown. In the analysis, the initial equivalent deflection and local buckling criterion of stub column are introduced. On the other hand, although several elaborate analyzes have been performed to make clear the interactive behavior, there is little agreement with each other. Therefore, a detailed comparison of those results has shown that the analysis using moment-thrust-curvature relations are in best agreement with Q-factor method, accuracy of which was confirmed by experiments. Accordingly, the validity of the proposed simplified analysis was examined by comparison with the analysis using moment-thrust-curvature relations.