基于Volterra理论的扁平箱梁气动力非线性特性研究

为了研究扁平箱梁断面气动力系统的非线性特性，采用Volterra理论和CFD方法，对丹麦大带东桥主桥加劲梁断面的气动力特性进行研究。利用脉冲激励模型分别作竖弯和扭转运动，并基于CFD一次数值模拟，对大带东桥扁平箱梁断面气动力系统的Volterra级数核进行识别，建立扁平箱梁断面气动力系统的非线性离散时间Volterra级数模型，该模型可以快速给出任意简谐激励下的气动力响应，无需耗时很久的CFD模拟。分别基于竖弯和扭转向的强迫简谐位移激励，使用Volterra级数气动力模型对大带东桥扁平箱梁断面的气动力系统进行仿真，将得到的仿真时程与CFD模拟结果进行对比，分析振动频率和幅值对扁平箱梁断面气动力系统非线性特性的影响。结果表明：忽略二阶及以上非线性高阶项得到的Volterra级数模型给出的气动力估计与CFD模拟差别很小；扁平箱梁断面气动力的高阶非线性效应较小，其为弱气动力非线性系统；在研究的强迫运动位移幅值和频率范围内，扁平箱梁断面的气动力模型响应没有表现出对振动幅值和频率的显著相关性，且仿真值与CFD模拟值的最大相对精度误差不超过10%。

Research on Nonlinear Aerodynamics of Flat Steel Box Girder Based on Volterra Theory

In order to investigate the nonlinear aerodynamic behaviors of the flat box girder,by Volterra theory and computational fluid dynamics (CFD) method,the aerodynamic behaviors of stiffness girder of the Great Belt East Bridge main span was investigated.Imposing the impulse displacement upon the model to undergo heaving and pitch motion,the Volterra kernels of aerodynamic system of the Great Belt East Bridge flat box girder was identified based on one run of CFD simulation.Then the discrete-time Volterra model with nonlinearity of the aerodynamic system of the flat steel box girder was established which can be employed to simulate aerodynamic response quickly to arbitrary harmonic inputs without time-consuming CFD simulations.The aerodynamic system of flat steel box girder cross section of the the Great Belt East Bridge was simulated, by using the present Volterra aerodynamic model. The aerodynamic forces time histories with the same imposed harmonic displacement excitation of the heaving and pitch motion were compared. The effects of motion frequency and amplitude on nonlinearity of the aerodynamic system of the flat steel box girder were also analyzed and evaluated. Within the present range of forced frequency and amplitude,there was no significant correlation of the aerodynamic model response on the frequency and amplitude.Moreover,the maximum deviation between the Volterra model and CFD was not more than 10%.The results show that the present Volterra models, ignoring the second-order and above high-order components, can provide aerodynamic estimations which agree well with the CFD simulations. The high-order aerodynamic nonlinearity is relative small,that is,the aerodynamic system of the flat box girder is of small nonlinearity.