箱梁非定常涡激力跨向相关性及其应用研究

The vortex-induced vibration (VIV) of long-span bridge is a three-dimensional (3D) problem along span. For the lack of knowledge and inadequate consideration about spanwise correlation of vortex-induced forces, when the sectional model (2D) test results are used to assess the VIV performance of prototype bridge (3D), misjudgment is always made in this situation.. This program is carried out based on the existing researches about spanwise correlation of vortex-induced forces and three-dimensional VIV analytical approaches for long-span bridges. Several section models of long-span bridge girder are made for surface pressure and wake speed measurement by using free vibration and forced vibration method. The influencing mechanism of spanwise correlation of vortex-induced forces is revealed, and the influence law of changing the span length to height ratio on vortex-induced force itself and its spanwise correlation is ascertained. The contributions to the correlation of overall vortex-induced forces made by aerodynamic acting on different positions of section and wake vortex are studied. After that, based on the taut-strip tests, and compared with several approaches, a simple way to get the correlation of vortex-induced forces by conventional test is found out. Finally, a practical 3D analytical approach which uses conventional section model tests to accurately estimate the vortex vibration response of the prototype bridge are proposed, and the validity of the proposed approach is verified by taut-strip wind tunnel tests.

大跨度桥梁的主梁涡激振动问题是沿跨向的三维问题。由于对涡激力的跨向相关性的认识和考虑不充分，在利用节段模型（二维）试验结果估计实际桥梁结构(三维)的涡振性能时，往往会造成对大桥涡振性能的误判。. 本项目将在已取得的涡激力跨向相关性研究成果及大跨度桥梁三维涡振分析方法的基础上，采用自由振动与强迫振动相结合的方式，在涡振锁定区开展一系列箱梁节段模型表面测压及尾流测速试验，揭示涡激力跨向相关性影响机制，探明模型展高比变化对涡激力本身及其跨向相关性的影响规律；研究断面不同位置气动力及尾流涡脱对断面整体涡激力相关性的贡献；然后，以拉条模型试验结果为参考依据，多方法对比，寻找一种可通过常规试验手段获得涡激力跨向相关性的试验方法；最后，建立一种利用常规节段模型试验便可准确估计实桥各阶模态下涡振响应的三维涡激振动实用分析方法，并通过拉条模型风洞试验进行验证。

涡激振动致振风速较低，是钝体结构上常见的一种限幅振动，容易引发桥梁结构疲劳破坏、行车舒适性等问题。大跨度桥梁的主梁涡激振动问题是沿跨向的三维问题， 在利用节段模型试验结果估计实际桥梁的涡振响应时需计入振型和涡激力跨向相关性的影响，其中涡激力跨向相关性是本项目研究开展的重点。.本项目选取了1:5矩形断面、大贝尔特东桥的引桥断面（梯形）以及流线型箱梁断面三种不同类型的典型钝体断面开展相关研究。采用自由振动与强迫振动相结合的方式，在涡振锁定区附近开展了大量的表面测压和测振试验，研究了几种钝体表面脉动压力分布特性、涡激力跨向相关性影响机理以及断面不同位置气动力对整体涡激力相关性的贡献。在已有研究成果的基础上对三维涡振分析方法进行了优化，编制了大跨度桥梁三维涡振分析程序。然后对利用常规节段模型试验结果预估实桥各阶模态下涡振响应的三维涡激振动方法进行了简化，便于工程应用。最后，利用矩形和梯形两种断面的节段模型和拉条模型风洞试验对本项目方法进行验证。.本项目的研究成果使大跨度桥梁的涡振响应计算更加合理准确，使大跨度桥梁抗风设计进一步得到完善，具有十分重要的科学意义和工程价值。