Effect of B/D Ratio of Section on Flutter and Buffeting of Long-Span Bridges

• Main Authors: Tsang-Lien Lan, 藍倉連
• Other Authors: Yuh-Yi Lin
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/02915150467998221852

碩士 === 淡江大學 === 土木工程學系 === 89 === The developments of bridge construction techniques and the improvements of high strength materials have made the modern bridges designed and built towards long spans with slender sections. Because these types of bridges are more flexible than the other types of bridges, they are more sensitive to wind excitations. The most significant aerodynamic phenomenon for long-span bridges includes flutter and buffeting. Self-excited forces, bridges induced by deck motions, will result in aerodynamic stiffness and aerodynamic damping. When the negative aerodynamic damping is equal to the structural damping at some wind speed, the flutter will occur, that is, the bridge will result in failure. Buffeting response is mainly induced by the wind turbulence. Flutter critical wind speed and buffeting of the bridge system are not only related to the geometry of bridge deck but also the width-depth ratio of the deck section. In this thesis, section model tests were conducted to investigate the effects of different width-depth ratios on flutter derivatives and wind force coefficients in smooth flow. Based on the test data, the critical wind speed and buffeting were then evaluated by using numerical analysis method. The results show that the changes of width-depth ratios have significant influence on aerodynamic stability of long span bridges. With the increase of width-depth ratio, the flutter critical wind speed and coupling effect will increase for streamline section. However, the changes of width-depth ratio have no significant influence on coupling effect for bluff sections. The width-depth ratios also affect buffeting responses on bridge structures. Therefore, effects of width-depth ratio of the deck section on aerodynamic stability should be taken into account in the bridge design.