A study on the effects of turbulence scale on flutter of long span bridges
Project/Area Number  01550367 
Research Category 
GrantinAid for General Scientific Research (C)

Allocation Type  Singleyear Grants 
Research Field 
土木構造

Research Institution  Research Institute for Applied Mechanics, Kyushu University 
Principal Investigator 
NAKAMURA Y. Research Institute for Applied Mechanics, Kyushu University, Prof., 応用力学研究所, 教授 (80038554)

CoInvestigator(Kenkyūbuntansha) 
HIRATA K. Research Institute for Applied Mechanics, Kyushu University, Research Associate, 応用力学研究所, 助手 (40199063)
OZONO S. Research Institute for Applied Mechanics, Kyushu University, Research Associate, 応用力学研究所, 助手 (10169302)
OHYA Y. Research Institute for Applied Mechanics, Kyushu University, Assistant Prof., 応用力学研究所, 助教授 (00150524)

Project Period (FY) 
1989 – 1991

Project Status 
Completed(Fiscal Year 1991)

Budget Amount *help 
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1991 : ¥200,000 (Direct Cost : ¥200,000)
Fiscal Year 1990 : ¥200,000 (Direct Cost : ¥200,000)
Fiscal Year 1989 : ¥1,800,000 (Direct Cost : ¥1,800,000)

Keywords  Long Span Bridge / Turbulence Scale / Flutter / Galloping / Buffeting / 大気乱流 / 自然風の乱れ 
Research Abstract 
Engineering structures such as long span bridges and tall buildings are exposed to highly turbulent wind. Since long span bridges are susceptible to flutter, e. g. galloping, torsional flutter, vortex excitation, etc., the effects of turbulence on flutter have been a longstanding problem. The ratio, L_x/h, of turbulence integral scale L_x to the body size h is one of the measures which identify the turbulence effect. In the present research, galloping of rectangular prisms is considered. The principal purpose is to comprehensively understand the effects of turbulence scale on galloping over a wide range of L_x/h. Not only 2D rectangular prisms but also 3D prisms with one end fixed to the wall (3D model) were used in order to attain larger values of L_x/h. Turbulent flows were generated by different grids with intensity u'/U about 10%, where u'is the r. m. s. of the ucomponent of velocity fluctuation and U is the free stream velocity. 2D model : Galloping is investigated on rectangu
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lar prisms with d/h of 0.63.0, where d is the depth and h is the height of the prism. (a) d/h=0.61.0 : Galloping occurs for both the uniform and turbulent flows with a slightly positive betaa, the aerodynamic growth rate of oscillation, where the scale effect is not significant. The oscillation due to buffeting is very weak. (b) d/h=2.0 : Galloping vanishes for the turbulent flows because of the promotion of reattachment of the separatedshearlayer to a side face, whereas galloping occurs for the uniform flow. With increasing L_x/h, betaa for the turbulent flows asymptotes to that for the smooth flow. This clearly shows that galloping is dependent on turbulence scale. (c) d/h=3.0 : Galloping vanishes for both the uniform and turbulent flows so that betaa negative. With increasing L_x/h, betaa decreases and tends to that for the uniform flow. 3D model : Galloping is investigated on rectangular prisms with d/h of 2.0 and 3.0. With increasing L_x/h, betaa for turbulent flows asymptotes to that for the smooth flow in a similar way to the 2D model. Buffeting : In addition to galloping, models with d/h=2.0 and 3.0 at high reduced flow velocities are suffered from buffeting in turbulent flows with large Lx/h. The amplitude of buffeting increases rapidly at L_x/h of 2.03.0, but beyond around 10.0, the amplitude approaches an upper hmit. Less

Report
(4results)
Research Output
(6results)