台风下大跨度斜拉桥钢桥塔动力性能实测研究

Field Measurement Research on Dynamic Performance of Steel Pylon of a Long-span Cable-stayed Bridge Under Typhoons

以南京大胜关长江公路大桥钢桥塔为对象,利用台风“温比亚”和“利奇马”途经桥址区时大桥结构健康监测系统的实测数据,探究了台风作用下大跨度斜拉桥超高钢桥塔动力性能的演变规律及其影响因素。首先,分析了台风期桥址区风速和温度的变化特征,据此探究了环境因素影响下钢桥塔位移和加速度响应的演变规律。然后,采用随机减量法识别了钢桥塔的自振频率和阻尼比等模态参数,据此研究了台风期间实测环境因素对钢桥塔模态参数的影响。研究结果表明:在风速较小的情况下,钢桥塔加速度响应随温度升高而略有增加,这与温度增加导致的结构刚度降低有关;当平均风速大于10 m·s-1时,风速成为钢桥塔加速度响应变化的主导因素,纵桥向加速度响应随风速增加明显增大;台风期间钢桥塔横桥向自振频率与温度、加速度呈负相关,与平均风速成正相关;台风期间钢桥塔纵桥向阻尼比与风速的相关性较显著,阻尼比随着风速的增加而增加。研究结论可为类似钢桥塔的抗风设计与安全评估提供科学参考。

Taking the steel pylon of Nanjing Dashengguan Yangtze River Highway bridge as the object,using the data measured by the bridge structural health monitoring system when typhoon Rumbia and Lekima passed through the bridge site,the evolutionary law of the dynamic performance of the ultra-high steel pylon of a long-span cable-stayed bridge under the influence of typhoons and the influential factors were investigated.Firstly,the variation characteristics of wind speed and temperature at the bridge site during typhoons are analyzed.Based on this,the evolution characteristics of the displacement and acceleration responses of the steel pylon under the influence of environmental factors are studied.Subsequently,the modal parameters including the natural frequency and damping ratio of the steel pylon are identified using the random decrement technique(RDT).Accordingly,the evolutionary law of the modal parameters of the steel pylon with the changed environmental factors during typhoons were analyzed.Results show that the acceleration responses of the steel pylon slightly increase with the increased temperature in the low-wind-speed range.The decreased structural stiffness with the increased temperature could be the main reason.When the wind speed is larger than 10 m·s-1,the wind becomes the dominant factor that changes the acceleration responses of the steel pylon.The longitudinal acceleration responses increase obviously with the increased wind speed.During typhoons,the natural frequency of the steel pylon is negatively correlated with temperature and acceleration,and positively correlated with the wind speed.The longitudinal damping ratio of steel pylon is correlated with the wind speed during typhoons and increases with the increased wind speed.The conclusions can provide scientific references for wind resistance design and safety evaluation of similar steel pylons.