Wind Tunnel Experimental Investigation On The Flutter Characteristic Of A Long Span Cable-stayed Bridge

With the development of modern materials, design theories and construction techniques, the cable-stayed bridge grow with longer span and more flexibility. The stiffness and damping ration of a cable-stayed bridge depress clearly, so flutter have a critical bearing on the design of it. Flutter is a kind of self-excited vibration induced by wind acting on structures. Flutter critical state will be the important feature of it,that is flutter critical frequency and critical wind.Contents of this paper are as follows: First of all, this paper introduces the basic theory of flutter and the finite element theory, calculation methord used on bridge structural dynamical characteristic, and apply the space finite element model to Finish the calculation of the full-bridge structure dynamic charactemistic. Secondly, the aerodynamic model of the bridge is carried out basing on the the similarity theory. It compares the self-vibrate characteristic of the actual bridge and bridge by field model test. It calculate flutter critical wind speed using the approximate formula and determine the stability of the bridge flutter. Thirdly, with someone coastal-span bridge as background, on the basis of wind tunnel test and the static test with sectional model, this thesis studies the steady aerodynamic characteristic of the main girder. On the basis of section model with dynamic test, it studies the flutter characteristic of the girder and determine it's critical wind speed for flutter. Flutter derivatives of the girder are identified also. The test results indicated that the critical wind speeds for flutter well above the test wind speeds for flutter were obviously higher than for the bridge. On the basis of full bridge aeroelastic model tests were also carried out to investigate its wind resistance stability .The test indicated that the bridge has well whole wind resistance capability. Since the bridge specificity (wind environment is complex, large span bridges etc.), decide to make a full bridge wind tunnel tests. Through the full bridge model wind tunnel tests (including the completion state, the largest single-cantilever state and the largest double-cantilever state), observed phenomena and measured flutter flutter critical wind speed.The test results show that there is no flutter when flutter critical wind speed of section model test's wind speed reach to 15m/s which conversion to a real bridge wind speed has reached to 134 m/s,there is also no flutter when flutter critical wind speed of full bridge model test's wind speed reach to 15m/s which conversion to a real bridge wind speed has reached to 98 m/s,both of them are much higher than the bridge flutter testing speed [Vcr] = 72.2m/s, it shows that the flutter stability of cable-stayed is good. Under the most unfavorable two construction states(the largest double-cantilever state and the largest single cantilever state)which converted to the actual bridge flutter critical wind speed is much higher than the bridge flutter test wind speed, therefore the flutter stability during the construction is processed.