桥梁节段模型气弹振动的非线性判别方法研究

在ERA(Eigensystem Realization Algorithm)的理论框架内建立了误差因子,评估桥梁节段模型风洞实验中气动导数的辨识质量。通过子空间能量分解,分别计算辨识过程中有效识别信号成分能量和未被识别信号成分能量与总信号能量的比值,并以此构造误差因子。将相同实验环境下自由衰减振动和尾流激励随机振动两组实验的误差因子相互比对,判断桥梁节段模型的气弹振动非线性是否对气动导数辨识结果产生影响。依据误差因子判断,在本文所使用的两种节段模型中,部分流线型箱梁断面具有较强的耦合非线性;而槽形开口型断面的模型具有较低的耦合非线性。

On the Nonlinearity Index for Aeroelastic Vibration of a Bridge Deck Sectional Model

Error indices were proposed within the framework of ERA (eigensystem realization algorithm) method to evaluate the quality of flutter derivatives identified via wind tunnel experiment of a bridge deck sectional model. By decomposing signal energy into subspaces, the energy ratios among the total signal energy and the effectively identified signal energy and the un-identified signal energy were calculated, respectively, two error indices were defined during the system identification process. Error indices were constructed based on above results. By comparing two sets of error indices obtained from the free attenuation vibration experiment and the wake turbulence-induced ambient vibration experiment performed under identical experimental conditions, respectively, the effect of nonlinearity on the identified flutter derivatives was evaluated based on the proposed error index. Results suggest that within two sectional models used in above mentioned two experiments, the partially streamlined box girder model shows a stronger index for nonlinearity, while the other bluff model with openings presents weaker nonlinearity.