| In recent years,China’s oil and gas transportation industry has developed rapidly,and the scale of its pipeline network has continued to expand.Due to its advantages of strong spanning ability,reasonable stress,and convenient construction,pipeline suspension bridges are often used in pipeline transportation projects.However,this type of structure has a large slenderness ratio and low rigidity,so it is extremely sensitive to wind loads.In areas where freezing rain is more severe,ice accretion will occur on the surface of the structure of the pipeline suspension bridge,which greatly changes the structural shape and quality of the structure,which may greatly affect its wind resistance.In order to study the aerodynamic characteristics and static wind response of pipeline suspension bridges before and after ice accretion,this paper first studies and summarizes the ice accretion shapes of various components of the pipeline bridge,and then develops the wind on various typical profiles of the pipeline bridge and the aerodynamic characteristics before and after ice accretion In the tunnel test study,the finite element method was used to study the static wind stability and influencing factors of the pipeline bridge.The main work and conclusions are as follows:(1)Through the ice accretion experiment,the effects of diameter,inclination angle and rainfall frequency on cylindrical ice accretion,as well as the influence of the arrangement of steel profile,rainfall frequency and size on ice accretion were studied.The results show that: The formation process of the ice shape of the horizontally placed pipelines can be summarized as: crescent-shaped → D-shaped → fan-shaped,The ice-covered shape of the obliquely placed round tubes is mainly crescent-shaped and fan-shaped;The radial ice accretion thickness,icicle length,and icicles lateral spacing of a horizontally placed pipelines are positively correlated with the diameter,and the ice coverage range is negatively correlated with the diameter;The ice accretion thickness of the inclined pipeline is negatively correlated with the inclination angle;when the inclination angle is less than 30°,the length and quantity of the icicles of the circular tube are negatively correlated with the inclination angle;after the inclination angle is greater than 30°,no icicle is generated,and the bottom forms a long sheet shape ice;There is no size effect on the thickness of the steel accretion.The length of the icicles is positively related to the size.(2)The results of the study show that the diameter of the pipe has a greater influence on the three-component force coefficient of the section;the double-pipe effect on the section is more obvious.The lateral spacing of the pipeline has a small effect on the aerodynamic force coefficients;the crescent-shaped ice coating has a small effect on the cross-section aerodynamic force coefficients,and the fan-shaped ice accretion has a large effect;the Reynolds number effect of the crescent-shaped ice accretion and the fan-shaped ice accretion is not obvious;(3)Taking the cross-section of a single-layer pipeline suspension bridge as the research object,through the finite element analysis,the effects of cable wind load,initial wind angle of attack,ice accretion shape and cable system setting method on static wind stability were studied.The results show that: The cable wind load will obviously increase the lateral displacement of the main beam and lead to a significant decrease in the static wind instability critical wind speed;Mid-span displacement of stiffening girder gradually decreases as the initial angle of attack changes from negative to positive,and the static wind divergence critical wind speed will gradually increase;both crescent-shaped ice and fan-shaped ice will greatly reduce the static wind divergent wind speed;the static wind instability configuration of the anti-wind cable is the instability of space bending and torsion coupling,and the design scheme of no wind cable occurs the lateral buckling instability. |
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