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Design method of frame structures with effective length based on eigen value analysis

基于特征值分析的框架结构有效长度设计方法

基本信息

批准号：
60850087
负责人：
HORII Hideyuki
金额：
$ 2.75万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1987
项目状态：
已结题

项目摘要

In the present design system for steel frame structures, the designers carry out the small displacement analysis and the design code covers the effect of geometrical nonlinearity. Hence the design code is complicated and incomprehensive. The provision on the effective column length is a typical example.In the present study, for the future design system based on nonlinear structural analyses, matters such as "what kinds of nonlinear analysis must be carried out?" or "what the design code must prescribe?" are investigated. Firstly, with a precondition that the safety and economy in the present design are maintained, the required nonlinear analysis is concluded to bo the linearized finite displacement analysis (LFDA). The design method with LFDA is investigated. It is shown that one of the problem in this method for bifurcation phenomena is solved by introducing appropriate effective initial imperfections for in-plane problem.For out-of-plane problem the design method based on LFDA is found to have numbers of difficulties to be cleared and the desing method based on the use of strength curve seems to be practical at this stage. However, the present design method includes ambiguity in the determination of effective column length of a general member. Here, the effective length is interpreted as a parameter shich represents the extent of the reometrical nonlinearity, and a new method to determine the effective length is proposed. The effective length is calculated from additional bending moment calculated by LFDA. The design with this method is shown to provide reasonable results.Finally, imperfections for out-of-plane problems are investigated, and 3-d befaviors of simple frame structures are analyzed. It is shown that the design based on LFDA is sensitive to the direction of the imperfections and the stiffness of the secondary members. The direction of the future study to establish design method with LFDA is pointed out.

在现行的钢框架结构设计体系中，设计人员进行的是小位移分析，设计规范考虑了几何非线性的影响。因此，设计规范是复杂和不全面的。关于有效柱长的规定就是一个典型的例子，在目前的研究中，对于未来基于非线性结构分析的设计体系来说，这样的问题就是“必须进行什么样的非线性分析？”或者“设计规范必须规定什么？”都进行了调查。首先，在保证设计安全性和经济性的前提下，进行了线性化有限位移分析所需的非线性分析。研究了采用LFDA的设计方法。对于平面外问题，基于LFDA的设计方法有许多困难需要解决，而基于强度曲线的设计方法在现阶段似乎是可行的。然而，目前的设计方法在确定一般构件的有效柱长时存在模糊性。本文将有效长度解释为表示折射率非线性程度的参数，提出了一种确定有效长度的新方法。有效长度由LFDA计算的附加弯矩计算得出。最后，对平面外问题的缺陷进行了分析，并对简单框架结构的三维性能进行了分析。结果表明，基于LFDA的设计对缺陷的方向和次构件的刚度是敏感的。指出了建立LFDA设计方法的未来研究方向。