1988 Fiscal Year Final Research Report Summary
Design method of frame structures with effective length based on eigen value analysis
| Project/Area Number |
60850087
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| Research Category |
Grant-in-Aid for Developmental Scientific Research
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| Allocation Type | Single-year Grants |
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| Research Field |
土木構造
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| Research Institution | The University of Tokyo |
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Principal Investigator |
HORII Hideyuki University of Tokyo, Faculty of Engineering Associate Professor, 工学部, 助教授 (10181520)
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| Co-Investigator(Kenkyū-buntansha) |
FUJINO Yozo University of Tokyo, Faculty of Engineering Associate Professor, 工学部, 助教授 (20111560)
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| Project Period (FY) |
1985 – 1987
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| Keywords | Design method / Geometrical nonlinearity / Effective length / Linearized finite displacement analysis / 固有値解析 |
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| Research Abstract |
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.
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Research Products
(11 results)
