不同风嘴形式分体箱梁桥梁的静力风致稳定性能

Stationary aerodynamic stability performance of twin box girder bridges with different wind fairings

作为大跨径以及超大跨径桥梁一种新兴的断面形式,分体箱梁可以改善空气动力性能和提高颤振临界风速,但是还需要保证其静力风致稳定性能,研究了不同风嘴形式下分体箱梁的静力三分力系数和静力风致稳定性能随开槽率的演变规律。结果表明:两种风嘴形式分体箱梁的阻力系数随开槽率增加而增大,采用断面实体宽度为无量纲化标准时断面升力系数绝对值会随开槽率的增加而增加,这与采用断面总宽为无量纲化标准时结果相反,升力矩系数绝对值会随着开槽率的增加而减小,但这种规律性会受到风攻角的影响;风嘴对称性的变化仅改变断面阻力系数随开槽率的变化规律;两种计算模型下,对称风嘴断面分体箱梁桥梁跨中的各向位移绝对值和静力风致失稳临界风速随开槽率的变化规律完全相反,而不对称风嘴断面的各向位移变化规律相似但也有区别;总体上对称风嘴断面的最低静力风致失稳临界风速要高于不对称风嘴断面;考虑结构刚度变化会使断面开槽后静力风致失稳临界风速随着开槽率的增加而升高并超过不考虑刚度变化时的相应值,故对分体箱梁静力风致稳定性能分析时需要考虑开槽率不同带来的结构刚度变化。

As a new sectional form of long-span bridges or super long-span bridge,twin box girders can improve aerodynamic performance and increase the flutter critical wind speed,but it is also necessary to ensure its stationary aerodynamic stability.The evolution laws of static force coefficients and stationary aerodynamic stability of twin box girders with different wind fairing forms were studied.Results show that the drag coefficients of twin box girders with two wind fairing forms may increase with the increase of slotting rate,and the absolute values of lift coefficients may increase with the increase of slotting rate when solid sectional width is adopted as the dimensionless standard,which is opposite to the observation when total sectional width is adopted as the dimensionless standard,and in the latter case,the absolute values of pitching moment coefficients may decrease with the increase of slotting rate.However,all the variation laws may be affected by the wind attack angles.Variations in symmetry of wind fairings only change the variation laws of the drag force coefficients with slotting rates.For two calculated models,with the slotting rate,the variation law of every absolute displacement responses at the mid-span and the variation law of critical wind speeds of stationary aerodynamic instability of a two box girder bridge with symmetrical wind fairings is completely opposite to each other,while the variation laws of displacements in all directions with asymmetric wind fairings are basically similar although some distinctions can still be observed.As a whole,the lowest critical wind speeds of stationary aerodynamic instability for twin box girders with symmetric wind fairings are generally higher than those with asymmetric wind fairings.The critical wind speeds of stationary aerodynamic instability may increase with the increase of slotting rate after sectional slotting if the change of structural stiffness is considered,and moreover the critical wind speeds may exceed the correspondingvalues if the change of structural stiffness isn＇t considered.Therefore,it is necessary to consider the change of structural stiffness due to the difference in slotting rates when analyzing the stationary aerodynamic performance of twin box girder.