山区峡谷大跨度钢桁梁悬索桥抗风性能研究

Study on Wind-resistance Performance of Steel Truss Girder Suspension Bridges in Mountainous Canyon

为了研究山区峡谷地形条件下某特大桥的风致振动特性和抗风性能,并据此采取气动措施确保大桥在施工和服役全周期的安全,针对桥址处山区峡谷地形特点,采用缩尺地形模型风洞试验对大桥风环境进行了全面探测并确定了设计风参数;采用弹簧悬挂节段模型风洞试验对主梁断面在大攻角范围内的颤振性能和涡振性能进行了评估,进而据此增设气动措施并对气动措施的抗风效果进行了全面检验;根据梯度风速等效原则建立了试验所测风速和桥址附近气象站基准风速的关系,并提出了此类情况下根据不同的风攻角区间合理确定颤振临界风速的方法。结果表明:由于山区峡谷地形的影响,该特大桥桥址处风攻角很大、而且风速和风攻角沿桥跨方向分布很不均匀;大桥主梁断面在较大负攻角下颤振临界风速较低,相对颤振检验风速富余度很小;大桥颤振性能控制设计,通过在主梁钢桁架桥面板设置气动稳定板可以提高主梁在负攻角下的颤振性能。经过多种气动稳定措施综合比选,该特大桥最终选用"主梁桥面板下方设置3道纵向永久稳定板+桥面上中央分隔带处设置1道施工期临时稳定板"的方式以提高主梁建设及运营期的颤振性能。

In order to study the wind-induced vibration characteristics and wind resistance performance of a grand bridge under mountainous canyon terrain condition,and to take aerodynamic measures to ensure the safety of the bridge during the whole construction and service periods accordingly,the wind environment of the bridge is comprehensively detected and the design wind parameters are determined by using scaled terrain model wind tunnel test according to the terrain characteristics of mountain canyon at bridge site.The flutter performance and vortex vibration performance of the girder section in the range of large attack angle are evaluated by spring suspension section model wind tunnel test,then the aerodynamic measures are added,and the wind resistance effect of the aerodynamic measures is comprehensively tested.The relationship between the wind speed measured by the test and the reference wind speed of the meteorological station near the bridge site is established according to the equivalent principle of gradient wind speed,and a method for determining the critical flutter wind speed according to different wind attack angles in this case is proposed.The result shows that(1)due to the influence of mountainous canyon topography,the wind attack angle of this grand bridge is very large,and the wind speeds and the wind attack angles are distributed unevenly along the bridge span;(2)the critical flutter wind speed of the bridge is smaller at larger negative attack angle,and the wind speed redundancy of relative flutter test is very small;(3)for the design of the bridge flutter performance control,the flutter performance of the main girder at negative attack angles can be improved by setting the aerodynamic stabilization plate on the main girder steel truss bridge deck.After comprehensive comparison and selection of different aerodynamic stability measures,the method of"3 longitudinal permanent stabilizing plates under the main girder deck+1 temporary stabilizing plate during the construction period at the central separation zone on the bridge deck"is selected finally for this grand bridge to improve the flutter performance of the main girder during construction and operation periods.