栏杆基石对闭口箱梁桥梁涡振性能影响的机理

为研究检修道栏杆基石对桥梁涡激振动性能的影响，依托中国某主跨808 m的超大跨度闭口箱梁加劲梁悬索桥，通过主梁大比例节段模型弹性悬挂测振测压风洞试验获取模型风致振动响应和表面各测点压力时程数据，测试原设计断面在±5°攻角范围内的涡振性能，对比分析3种不同栏杆基石位置和高度工况下主梁涡振响应性能和桥面测点脉动压力系数均值、均方差、压力功率谱以及局部气动力和总体气动力的相关性。研究结果表明：依托工程主梁设计断面发生了显著的竖向和扭转涡激共振，且扭转涡振显著超出规范允许值，主梁涡振性能随来流风攻角的增大而变差。主梁表面实测脉动压力数据分析显示，由于栏杆和基石的阻挡，箱梁上表面气流分离后在后部再附，导致上表面前部和中后部发生了强烈的压力脉动。上表面前部、后部以及下表面迎风区斜腹板局部气动力与总体气动力具有很强的相关性，这也是导致主梁发生显著扭转涡振的根本原因。将栏杆基石移至桥面板边沿显著减小了上、下表面压力脉动，上表面前部和后部气动力相关性被破坏，可以大幅抑制涡振；将栏杆基石移至桥面板边沿，并降低栏杆基石高度抑制了气流在上表面后部的再附现象，断面压力脉动被削弱，局部气动力和总体气动力相关性被完全破坏，从而有效抑制涡振。

Mechanism of the Influence of Railing Cornerstone on Vortex-induced Vibration of Closed Box Girder Bridge

In order to investigate the influence of railing cornerstone on the vortex-induced vibration (VIV) performance of a bridge, taking a super long-span closed box girder suspension bridge with main span 808 m as engineering background, a wind tunnel test was conducted to obtain the VIV response and pressure time-history data from pressure measurement points on a large-scale section model. The VIV performance of the originally designed cross-section at an attack angle of ±5° was tested. The mean value, mean square deviation, pressure power spectrum, and correlation between the local aerodynamic force and overall aerodynamic force of the bridge-deck measurement points under three different working conditions were compared and analyzed. The results show that significant vertical and torsional VIV occurred in the designed section of the main girder, and the torsional VIV significantly exceeded the allowable value of the code. The VIV performance of the main girder decreased with increasing angle of attack of incoming wind. The analysis of measured fluctuating pressure data on the main girder surface showed that, owing to the barrier of railings and cornerstones, the air flow on the upper surface of the box girder separated and then attached to the back, resulting in strong pressure fluctuations at the front, middle, and rear parts of the upper surface. The research results indicated that the fundamental cause of torsional VIV is the strong pressure fluctuations at the front and rear of the upper surface of the girder. The local aerodynamic forces of the oblique web in the windward zone of the upper surface, the rear, and lower surface are strongly correlated with the overall aerodynamic forces. The pressure fluctuations on the upper and lower surfaces were significantly reduced by moving the railing cornerstone to the edge of the bridge deck. The aerodynamic correlation between the front and rear parts of the upper surface is destroyed, which can greatly suppress the VIV. With the reduction of railing cornerstone height, the reattachment to downstream regions of the upper surface was enormously restrained. The pressure fluctuations in the section was weakened, and the correlation between local aerodynamic force and overall aerodynamic force is completely destroyed, thus effectively suppressing the VIV.