| Summary: | 碩士 === 國立中興大學 === 土木工程學系所 === 98 === In this study, I investigated the eccentricity effect on the aerodynamic instability of a suspension bridge. The experiments were conducted in Wind Tunnel Laboratory of the Agricultural Experimental Station of the National Chung Hsing University. I used a simple rectangular cross-section model as a bridge’s basic body shape. The effect on the dynamic reaction of the bridge plate is investigated based on a two-dimensional approach. In the uniform flow field, measurements of the dynamic reaction of the bridge plate by changing the flow speed, frequency ratio and eccentric mass site.
On the premise that the first mode (heaving direction) of the frequency is constant, at the different frequency of the conditions, the eccentric mass will cause of interaction effects on the bridge. The interaction effects are analyzed by the vertical displacement of root-mean-square and the changes to the degrees of torsion direction of root-mean-square.
According to the experimental results, I found out that at the same eccentricity of the conditions, the flutter critical velocity increases with the frequency ratio increases. At the same frequency of the conditions, the maximum of flutter critical velocity is in the downstream eccentric mass site, next is in the non-eccentric mass site, and the minimum of flutter critical velocity is in the upstream eccentric mass site. However, when the frequency ratio is 1.2, the response tendency is diversity while to compare the response tendency of the upstream and downstream eccentric mass site with other frequencies ratio.
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