桥梁断面范德波尔振子涡激气动力模型参数非线性化的能量原理

Energy mechanism used for non-linearization of vortex-induced aerodynamic loading model of bridge deck sections

采用范德波尔振子类涡激气动力模型,通过能量平衡原理,推导了涡激共振过程中结构的振幅增量、初始气动阻尼、非线性气动阻尼三者之间的基本关系,进而得出模型中气动力参数ε与振幅yT之间关系的识别原理。基于某扁平箱梁桥梁断面的节段模型涡振试验结果,对范德波尔类涡激气动力模型参数随振幅的演变关系进行了识别。结果表明,在涡激共振锁定区间内,随着振幅的增加,参数ε呈单调下降的趋势。与之相反的是,参数ε形成的非线性气动阻尼比却呈非线性增长的规律。当参数ε相关的非线性气动阻尼、初始气动阻尼、结构阻尼三者之和为零时,结构达到稳定的涡振极限环状态。研究表明:初始气动阻尼特性决定了结构能否起振而形成涡振锁定区间;识别出模型参数随振幅的变化关系后,高于试验阻尼的结构涡振响应具有可预测性。

Concerned with the Van der Pol type model of vortex-induced aerodynamic loading,fundamental relations among the structural motion amplitude,initial aerodynamic damping,amplitude-related aerodynamic damping are deduced according to the en-ergy balance principle.Further,the basic identification mechanism is obtained in terms of the relation between parameterεand mo-tion amplitude yT.Based on experimental results of vortex-induced response of a sectional model,which has a typical flat box girder configuration,the relations between the model parameters and the structural motion amplitude are identified.The results indicate that,within the vortex-induced lock-in range,εdecreases almost monotonously as the structural amplitude yT increases.On the contrary,the effective damping induced by theε-related term increases as yT increases.The structure reaches a steady limit-cycle-oscillation state when the three damping components,including the structural,ε-related and initial aerodynamic,neutralize com-pletely.The research of this work shows the initial aerodynamic damping properties determine if vortex-induced resonance is able to be excited and form a lock-in range.Once the relation between the model parameter and the structural amplitude has been identi-fied,the vortex-induced responses of structural damping ratios less than the one used for identification become predictable from the known parameter-amplitude relation.