1997 Fiscal Year Final Research Report Summary
STUDY ON SUPPRESSION OF AERODYNAMIC VIBRATIONS OF BUNDLE CABLES FOR SUPER LONG CABLE-STAYED BRIDGE
| Project/Area Number |
08455211
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
構造工学・地震工学
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| Research Institution | KYUSHU INSTITUTE OF TECHNOLOGY |
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Principal Investigator |
KUBO Yoshinobu KYUSHU INSTITUTE OF TECHNOLOGY,ENGINEERING,PROFESSOR, 工学部, 教授 (70093961)
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| Co-Investigator(Kenkyū-buntansha) |
KATO Kusuo KYUSHU INSTITUTE OF TECHNOLOGY,ENGINEERING,RESEARCH ASSISTANT, 工学部, 助手 (60039138)
YAMAGUCHI Eiki KYUSHU INSTITUTE OF TECHNOLOGY,ENGINEERING,ASSOCIATE PROFESSOR, 工学部, 助教授 (90200609)
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| Project Period (FY) |
1996 – 1997
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| Keywords | CABLE-STAYED BRIDGE / CABLE / AEROELASTIC VIBRATION / WAKE GALLOPING / SUPPRESSION METHOD / SURFACE PRESSURE / 3 COMPONENTS OF AERODYNAMIC FORCES |
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| Research Abstract |
The present research deals with suppression of aerodynamic vibrations of cables for a cable-stayd bridge.A multi-cable system for cable-stayd bridge inherently induces wake galloping due to wake of a windward cable. Although a lot of studies have been conducted to suppress the wake galloping, a good solution have not yet been found. In the present study, after making clear the mechanism of wake galloping, the new cable system was proposed. It was named as a closely and rigid connected cable. According to the mechanism made clear in the present study, when the interval both cables less than 3.56D (D is a diameter of cable), a hard type wake galloping occurs and when the interval is larger than 3.56D,a soft type wake galloping occurs. The value of 3.56D is strongly related with Karman's vortex street theory. Since the wake galloping was induced by the reason that the leeward cable existed in a region where the wake of the windward cable affected leeward cable, it was considered that it was possible to suppress the wake galloping by putting the leeward cable closely to the wind ward cable in order to get rid of influence of wake of the windward cable. Even if the leeward cable was put with interval of 1.3D,the wake galloping occurred in relatively small amplitude. Therefore, it was proposed to rigidly connect both cables to restrict the vibrating motion of leeward cable by the motionless windward cable. As a result of the experiments, it was made clear that the optimum interval between both cables was I.25D to reduce the aerodynamic amplitude of the closely connected cables. In order to understand the vibration mechanism, 3-component of aerodynamic forces and surface pressure at rest and vibrating states were measured. The proposed cable system was used for the lkara bridge that is the PC cable-stayd bridge with the longest span length in Japan.
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