Study to Clarify The Mechanism of Uniquely Large Horizontal Bridge Response Located in The Wake of aHill

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 13650526
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 構造工学・地震工学
• Research Institution: Kyushu Institute of Technology
• Principal Investigator: KIMURA Kichiro Kyushu Institute of Technology, Engineering, Associate Professor, 工学部, 助教授 (50242003)
• Co-Investigator(Kenkyū-buntansha): KATO Kusuo Kyushu Institute of Technology, Engineering, Research Associate, 工学部, 助手 (60039138) ; YAMAGUCHI Eiki Kyushu Institute of Technology, Engineering, Associate Professor, 工学部, 助教授 (90200609) ; KUBO Yoshinobu Kyushu Institute of Technology, Engineering, Professor, 工学部, 教授 (70093961)
• Project Period (FY): 2001 – 2002
• Keywords: Wind-induced vibration / Buffeting / Wake / Fluctuating wind velocity / Isolated hill / Bridge under construction / Split-film probe / Wind tunnel experiment

Research Abstract

This study was conducted to clarify the mechanism of uniquely large horizontal response observed with a bridge model located in the wake of an isolated hill.
The bridge and hill models were simplified as a cantilever and a cone. The location of the bridge model in the wake of the hill and horizontal skew angle were varied and responses were measured. The diameter of the hill was 4.5H, taking H as the height. The length of the cantilever model was H and it was located at height of 0.123H. The horizontal response became large when the model when the model was located around 3.3H leeward from the hill center. Also the response became large when the cantilever model had wind skew angle of 40 degrees. The kurtosis of the response sometimes reached to 4 to 4.5. With a series of flow visualization experiment, the formation of conical vortices that has the axis with skew angle of 40 to 50 degrees was suggested, and these vortices were thought to be the possible cause of large horizontal response.
Then the response and fluctuating wind velocity were measured simultaneously, and conditional sampling based on the occurrence of large responses was conducted to clarify the fluctuating wind velocity characteristics causing the large response. These were some cases where fluctuating wind velocity that acts on the bridge model with skew front line of around 40 degrees caused large responses, and that was considered to correspond to the vortex structure suggested in the flow visualization experiment.
On the other hand, there were other cases where these fluctuating wind velocity characteristics were not observed, or reproduction of the experimental results was not good. The cause is now sought considering sensitive effects by flow condition etc. Also the aerodynamic force characteristics are to be measured using simultaneous pressure measurement experiment.