基于监测数据的跨海斜拉桥强/台风作用效应研究

Strong wind effects on a sea-crossing cable-stayed bridge based on monitoring data

风是大跨、轻柔结构的主要影响荷载之一。基于2007～2012年6年间的监测数据研究了东海大桥主航道斜拉桥在5次台风和1次强风期间的极端风环境、结构振动响应以及结构动力特性的变化规律。研究发现，强／台风期间，桥址区风场的10min平均风速、脉动能量远大于正常情况，但湍流强度、积分尺度、阵风因子的变化规律不明显，这可能与10min统计时距偏长有关；强／台风期间的结构动力响应不同于低风速时以车辆荷载效应为主的正常情况，特别是结构侧弯振动加速度与竖弯、扭转振动相比有明显增加；强风对结构激励的卓越频率低于车辆荷载；强风期间结构模态频率的离散性变大而阻尼比有增加的趋势。该成果可以为大跨度跨海桥梁抗风设计和气动响应特性评估提供实测依据。

Wind loading is critical for long-span and flexible bridges. Based on the field measurement data from its Structural Health Monitoring System （SHMS） over a six-year period from 2007 to 2012, the extreme wind environment during strong winds and the wind loading effects on the dynamic responses and modal parameters of the Main Navigational Channel Bridge （MNCB） of Donghai Bridge at Shanghai are studied. The results demonstrate that during windy days, the 10-min mean wind speed and the turbulent variance are much larger than those in normal days, while the turbulence intensity, the integral length scale and the gust factor do not show a clear tendency. This might suggest that the average time duration of 10-min be too long for strong winds. The wind-induced dynamic responses also differ from those induced by the operating traffic loads, especially for the lateral vibration which is more sensitive to the wind than the vertical/ torsional modes. The dominant frequency contents of wind are lower than those of traffic. The damping ratios increase while the modal frequencies become scattered during strong winds. These research results can provide reference for wind- resistance design and aerodynamic performance evaluation of long-span bridges in ocean environment.