| Summary: | 碩士 === 淡江大學 === 土木工程學系碩士班 === 100 === In general, the investigations of aerodynamic behavior of bridges were established based on the assumption that the mean wind direction was normal to the longitudinal axis of bridge decks. In fact, the mean wind direction is rarely orthogonal to the bridge axis. Furthermore, some studies indicated that the aerodynamic responses of bridges under special wind direction and wind angle of attack maybe more significant than those in the case of zero angle of wind direction.
This paper aims to study the aerodynamic behavior of bridges under skew wind by performing a series of section model tests and a numerical analysis. Two types of deck cross sections, with the width-to-depth (B/H) ratios of 5 and 10, were used in the test and the numerical analysis. The section model tests included measurements of the aerodynamic coefficients and flutter derivatives, the flutter critical wind speeds, and the buffeting responses. The effects of yaw angles were investigated both in the tests and in the numerical analysis.
The experimental results show that for the section model with B/H ratio of 5, the lowest flutter wind speed occurs at a negative angle of wind attack and a zero yaw angle. For the section model with B/H ratio of 10, the lowest flutter wind speed occurs at a negative angle of wind attack and a yaw angle of 20 degrees. Both the experimental and numerical results indicate that in the case of zero angle of wind attack, the flutter critical wind speeds increase with the yaw angles and the buffeting responses decrease as the yaw angles increase.
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