特异风场风速特性对典型桥梁断面的作用机理研究

The extreme climate events induced by the non-synoptic winds, such as tornados, downburst, occurred more frequently with the change of global climate, which constitute new challenges to wind-resistant of bridges. However, the current wind-resistant design methods and specification are based on the normal climate. Thus it is quite essential to research the effects of non-synoptic winds on bridges, which has been also one of the most attractive and frontier issues in wind engineering. In this research, actively-controlled wind tunnel tests and CFD numerical simulations are carried out to investigate the effects of the speed characteristics of non-synoptic winds on the aerodynamic behaviors of rectangular and streamlined deck sections. Particular attention is devoted to the effects of strong velocity shear, transient characteristics. Time-averaged and unsteady flow structures, nonlinear aerodynamic forces, as well as temporal and spatial distribution of wind loads on the section are studied to enhance understanding the action mechanism of speed characteristics and propose the corresponding aerodynamic measures. This project will be not only helpful to fully understand the influence of non-synoptic winds on the aerodynamic behaviors of bridges, but also provide a certain scientific basis to improve the wind-resistant design method and code for long-span bridges.

全球气候持续变暖致使龙卷风、下击暴流等极端特异风频繁发生，给桥梁等结构抗风安全提出了新的严峻挑战。而目前大跨桥梁抗风设计方法和规范均是针对良态气候风环境，因此了解特异风作用下的桥梁抗风性能就变得尤为迫切，也已成为全球风工程界广泛关注的前沿热点问题之一。本项目针对特异风场中易导致灾变的强速度剪切特性和气流突变特性，选取典型扁平矩形和流线箱梁断面为研究对象，利用多风扇主动控制风洞和三维数值仿真算法，开展试验和数值研究；通过分析断面周围流场结构、非线性气动力效应、气动力时空分布特性等关键信息，明确特异风速特性的作用机理，构建面向工程应用的新型气动荷载模型，提出相应气动对策措施。本研究将助于全面了解特异风对桥梁结构的气动效应，并可为改善桥梁抗风设计方法提供一定科学参考依据。

随着全球气候的持续变化，以龙卷风、下击暴流等特异风为代表的极端特异气候频繁发生，且明显呈现逐年增多趋势。这给桥梁、高层建筑等风敏感性结构的抗风安全提出了新的严峻挑战。.本项目针对特异风场中易导致灾变的强速度剪切、气流突变等风速特性，以典型桥梁断面为研究对象，利用多风扇主动控制风洞和三维数值仿真算法，系统研究这些特异风速特性对断面气动特性的影响。研究表明，在剪切来流作用下矩形断面或桥梁断面高速侧的分离旋涡尺度增大，而低速侧的分离旋涡被抑制，导致高速侧和低速侧的流动再附点分别向上游和下游移动，但St数几乎不受来流剪切特性的影响。在正弦突变气流下，桥梁断面尾流区的旋涡脱落明显被抑制，相应的涡激力明显消失，但对断面自激力的影响较小，即自激力几乎不变。.本项目研究成果有助于理解特异风场风速特性对桥梁结构抗风性能的影响，并且可为改善桥梁抗风设计方法、完善抗风规范提供一定的参考依据，具有重要的科学意义和工程实用价值。