1995 Fiscal Year Final Research Report Summary
Evaluation of Residual Strength of Offshore Structures
| Project/Area Number |
05452313
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
海洋工学
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
YAO Tetsuya Hiroshima Univ., Faculty of Eng., Professor, 工学部, 教授 (20029284)
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| Co-Investigator(Kenkyū-buntansha) |
KITAMURA Mitsuru Hiroshima Univ., Faculty of Eng., Ass.Prof., 工学部, 助教授 (40195293)
FUJIKUBO Masahiko Hiroshima Univ., Faculty of Eng., Ass.Prof., 工学部, 助教授 (30156848)
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| Project Period (FY) |
1993 – 1995
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| Keywords | Offshore structure / Dent damage / Crack damage / Residual strength / Tubular member / Idealized structural unit method / Residual stress / Crack extension |
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| Research Abstract |
Residual strength of offshore structures which experienced denting damages, overall bending damages and cracked damages was investigated through a series of collapse tests and FEM shell analyzes on damaged tubular members. Based on the results, several improvements were made on the existing models of the Idealized Structural Unit Method (ISUM) for damaged tubular members.
From the bending collapse tests and FEM analyzes on tubular specimens with denting damages, it has been found that a significant magnitude of residual stress is induced during indenting process and this results in a large reduction of member stiffness when dented region is loaded in tension. When the dented region is loaded in compression, a load carrying capacity is mostly reduced, while in tension it may be recovered up to the ultimate strength of intact members because of the decrease of dent depth under the action of tensile load. However, deformations and local strains are large compared to the intact condition. The ISUM was improved so as to consider the reduction of stiffness and the change in dent depth for the case of dented damage loaded in tension, and the validity was demonstrated through a comparison with tested and FEN results.
Bending collapse tests, tensile collapse tests and the related FEM shell analyzes were performed on tubular specimens with a circumferential trough-thickness crack. The existing ISUM for cracked tubular members were also improved so that the effect of local yielding at crack tip can be considered in stiffness calculation.
Using the improved ISUM,several examples including plane frames and space frames having damages were analyzed and the effects of damaged on the load-carrying capacity of structures were investigated.
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