Research On Aerodynamic Interference Effects Of Buffeting Response Of Long-span Continuous Rigid Frame Parallel Bridges

With the successful implementation of the western development strategy,China's transportation construction has entered a great development.In order to meet the economic and social development of the increasing traffic demand,the form of the up-downgoing parallel separated twin brigdes are ofen used in high grade highway.The high pier and long span continuous rigid frame bridges become the preferred bridge across the high mountains and lofty hills.In contrast to the single bridge,the upper upstream of the double deck bridge may produce large wake vibration under strong winds,and the dynamic response of the downstream bridge may be enhanced or may be inhibited.Therefore,it is of great value to study the interference effect of wind-induced vibration of double deck bridge.In this paper,a bridge is used as the engineering background.Firstly,long-span continuous rigid frame bridge in the construction process may occur security issues.The root mean square and the mean value of the lateral displacement response of cantilever beam are studied respectively.Through the construction phase of the largest double cantilever state of the aeroelastic model wind tunnel tests,we get the data in response to single or double bridge in C terrain under turbulence flow displacement.And 5 influence factors,such as the net spacing of the main girder,the wind angle,the wind angle of attack,the direction of the bridge and the height difference,are analyzed.The results show that the aerodynamic interference effect of downstream bridge is greater than that of the upstream bridge.When the perturbed model is located upstream,the root mean square interference factor of the lateral displacement of the left cantilever end of the girder is 0.71~18.8,and the mean interference factor of the lateral displacement of the right cantilever is-4.3~1.45.When the perturbed model is located downstream,the root mean square interference factor of the lateral displacement of the left cantilever end of the girder is 0.7~25.8,and the mean interference factor of the lateral displacement of the right cantilever is-2.46~3.22.According to buffeting theory and dynamic characteristics of bridge,buffeting force at the root of the main beam and the bottom section of the pier is calculated by Midas Civil for single or double bridge in the construction of the largest double cantilever state.The quantitative law of aerodynamic interference effect of buffeting force is obtained.The results show that when the upstream bridge is close to the upstream bridge,the buffeting forces of the main beam root are generally reduced,under the condition of the lower net spacing=2m,the desolation along bridge=4m,and the height difference=1.2m.Therefore,the interference factor is far less than 1.But in the local position at 3 degrees angle of attack,the buffeting forces of the root of the main beam and the bottom of the pier are amplified by the interference effect,and the interference factors can reach up to 6.72 and 2.68 respectively.The results of this study show that in the analysis of wind resistant design of large span bridges,we should fully consider the adverse effect of the amplification effect of the parallel bridge aerodynamic interference effect.The experiment and analysis results in this dissertation can provide the reference for the wind resistant design of large span continuous rigid frame parallel bridges.