Control Of Vortex-induced Vibration Of Municipal Suspension Bridges With Single Cable Plane

As the natural frequency of long-span suspension bridges with steel beam is smaller than other types of bridges, vortex-induced vibration can easily occur in the design wind speed when main beam’s section is blunt and the bridge’s damping is low. As for municipal bridges, the existence of sidewalks adds blunt of main beam’s section, making it more susceptible to vortex-induced vibration. Even though vortex-induced vibration has no major damage on the bridge, but it creates a great deal of discomfort for people walking past it. Although our country’s research on suppression of vortex-induce vibration is in the leading position in the world, nevertheless it only focuses on the safety considerations which are the conditions that the amplitude of vortex-induced vibration is larger than the value of the standard. But as for the condition that the amplitude is smaller than the value of the standard, there are very few studies. Almost all the present studies for comfort are referred to foreign specifications.In this paper, the theory of the vortex-induced vibration and methods of damping are studied for a suspension bridge with single cable plane. The following task has been performed:(1) The history about wind-resistant of some bridges were reviewed, the necessity of wind-resistant for municipal bridges was pointed out. Then several comfort evaluation indexes and three kinds of specification codes about comfort evaluation were proposed.(2) FEM software was used for simulating the bridge, and then the simulation results were used in design of wind tunnel tests of1:50in XNJD-1wind tunnel. Because the amplitude of vortex-induced vibration of original design is larger than the value of the standard, eight kinds of aerodynamic shape optimization were tested to solve the problem of vortex induced vibration.(3) As the original design of vertical vortex-induced resonance amplitude is greater than the allowable value, we study the TMD system solutions to suppress vortex-induced vibration. TMD vibration control design not only can suppress the vertical vortex-induced vibration, but also can meet the comfort requirements.(4) The comfort evaluation index and three kinds of specification codes that are referred above are used in comparing original design, aerodynamic shape optimization and TMD vibration control design. Results show that aerodynamic shape optimization and TMD vibration control design both met the comfort requirements. But with broad comparison, aerodynamic shape optimization design is optimal design.