Numerical Simulation And Aerodynamic Optimization Of Vortex-Induced Vibration Of A Long-Span Suspension Bridge

With the swift social-economic development and the national strategical promotion,the incremental numbers and the rising span of long-span bridge-building are compounded for increased wind sensitivity,and the vortex-induced vibration(VIV)on bridges induced by improper usage of temporary maintenance facilities have been reported frequently.Thus,the VIV performance of bridges during service and maintenance as well as the impact of temporary maintenance facilities(such as water-filled barriers)deserves attentions.In recent years,the rapidly developing computational fluid dynamics technology has broad application prospects in VIV numerical simulation.Consequently,it is introduced to analyze the VIV performance of the streamlined box girder and its aerodynamic control optimization based on the Jiangyin Bridge,the first large-span suspension bridge over 1,000 meters in China.The main research contents are as follows.(1)Numerical simulation and mechanism analysis of vortex-induced vibration of a rectangular1:4 cylinder.Considering the similarity between the 1:4 rectangular section and the box girder section,numerical simulations of the VIV performance of the rectangular section based on CFD have been carried out.Subsequently,the dynamic grid and overset grid techniques are used to analyze the differences between the simulation results from the perspectives of vortex-vibration response and flow characteristics.The advantages of the overset grid technique are compared by the dominant frequency,Strouhal number,size,and positions of separation bubbles,as well as other main parameters,and the validity of the simulation results is verified on the ground of the existing wind tunnel tests.(2)Numerical simulation and analysis of vortex-induced vibration of streamlined box girder during service and maintenance.The overset grid model of the streamlined box girder of Jiangyin Bridge is established.Moreover,the sensitivity analysis of aerodynamic parameters of the box girder is executed from three aspects: component area shape,different area grid scale,and time step,and the accuracy of the numerical model are validated by wind tunnel test results.Owing to the high VIV risk on bridges caused by inappropriate usage of temporary maintenance facilities,numerical simulations of streamlined box girder VIV with additional water-filled barriers are carried out,and the main characteristics such as peak response and wind speed lockin interval are analyzed.On this basis,the VIV responses of different scale ratios and damping ratios are studied,and the rationality of the calculated parameters is illustrated.(3)Influence mechanism of water-filled barrier parameters on vortex-induced vibration performance of streamline box girder.The arrangement of the water-filled barrier destroys the sectional symmetry of the streamlined box girder.Thus,the influence of different locations,distances,and heights of the water-filled barrier arrangement on the VIV performance of the box girder is analyzed.Simultaneously,the periodic variation characteristics of vertical and torsional VIV surface wind pressure coefficient of streamlined box girder have been studied.The vorticity development process of streamline box girder has been described based on the second-generation vortex identification method Q criterion.Also,the influence on main vorticity distribution and trailing vorticity shedding mode is analyzed.(4)Aerodynamic shape optimization of the water-filled barrier for suspension bridges during service and maintenance.By adding through openings to the water-filled barrier,the VIV performance of the box girder in the service and maintenance period is studied.Additionally,the influence mechanism of the size,shape,and locations of the through openings on the vorticity development process and the surface wind pressure coefficient is investigated.The influence of different through openings forms on the VIV performance of streamlined box girder with the water-filled barrier is explored,by continuously adjusting its aerodynamic shape.Afterwards,the optimization scheme of water-filled barrier for suspension bridges during service and maintenance is proposed.