大跨度桥梁气动自激力的非线性时域模型和非定常特性研究

In view of the limitation of the existing linear model of the self-excited forces in the time-frequency domain, wind tunnel testing to measure the self-excited forces of bridge decks is proposed based on the free-vibration technique of sectional model. The nonlinear and non-steady characteristics of the aerodynamic forces of the bridge deck are investigated based on the testing result of the forces in the wind tunnel. Furthermore, a proper and effective nonlinear model of the self-excited forces of the bridge decks is proposed and the aerodynamic coefficients of the nonlinear model are extracted from the result of the forces with the non-coupling and coupling free-vibration wind tunnel test. The reliability and applicability of the nonlinear model is proved based on the forces measured from the free-vibration testing with large torsional amplitudes at the stable state and at the flutter state. Moreover, the nonlinear analysis of coupled flutter of long-span bridges is developed based on the proposed nonlinear time-domain model of the self-excited forces of the bridge decks and the research of the proposed project has hence important theoretical and practical significances.

鉴于现有时域-频域混合的线性气动自激力模型所存在的局限性，本课题通过开发一套采用节段模型自由振动方法测试桥梁断面气动自激力的风洞试验技术，提出气动自激力的自由振动风洞试验测试方法。基于节段模型气动自激力的风洞试验结果对主梁断面气动自激力的非定常特性和非线性特性进行研究。在此基础上探索建立适用有效的桥梁断面非线性气动自激力数学模型，采用非耦合和耦合自由振动测试的气动自激力对该数学模型的参数进行识别，并通过典型桥梁主梁断面在颤振前和颤振发生后大攻角振动状态测试的气动自激力试验结果对该非线性时域数学模型的可靠性和适用性进行验证。结合所提出的桥梁断面气动自激力非线性时域数学模型，进一步发展大跨度桥梁结构三维非线性颤振分析的实用理论和分析方法，本课题对大跨度桥梁抗风理论的发展具有重要的理论和实用意义。

对于实际桥梁非流线形断面，桥梁结构颤振和抖振都是具有非定常和非线性特性的复杂风致振动现象，线性化气动自激力模型已经难于满足大跨度桥梁结构颤振和抖振精细化分析的需要，有必要建立适应性和可靠性均较高的非线性气动自激力数学模型以及相应的的全桥三维非线性颤振和抖振分析实用理论和方法。.首先，研制了小型高精度高灵敏度动态三分量测力天平测力装置和测力传感器及其配套信号放大系统，此测力测振系统的设计比较好地解决了动态测力技术的瓶颈，对典型大跨度桥梁扁平箱梁断面的气动自激力进行了风洞试验测试。其次，基于不同振幅激励和不同来流风速情况下薄平板断面和桥梁扁平箱梁断面气动自激力的风洞试验测试结果，对薄平板和扁平箱梁断面气动自激力的非定常特性和非线性特性的变化规律进行了研究。在此基础上，建立了适用有效的桥梁断面气动自激力的非线性数学模型。提出了基于能量等效原理的三步自适应最小二乘建模方法，识别桥梁断面非线性数学模型各个气动参数，并对识别方法的适用性和有效性进行验证。结合所提出的桥梁断面气动自激力非线性时域数学模型，进一步发展了大跨度桥梁结构三维非线性颤振分析的实用理论和分析方法。最后，鉴于现有桥梁颤振理论方法和气动导数耦合自由振动识别方面存在的主要缺陷，通过建立了一种新的桥梁断面气动自激力数学模型，从根本上了克服Scanlan桥梁颤振理论方法的主要缺陷。