典型流线桥梁断面缩阶微分方程抖振气动力模型

Reduced differential equation aerodynamic buffeting model of typical streamlined bridge cross-section

目前的桥梁断面气动力理论框架中,气动力通常采用Scanlan线性准定常公式和Davenport气动导纳概念对准定常抖振力进行修正。已有的研究表明,导纳函数随来流特性变化较为明显,对同一桥梁断面也没有统一适用的导纳函数表达。除此之外,抖振力非线性特性方面的理论研究亦为国际风工程前沿热点问题。结合上述两方面,以桥梁抖振分析的关键问题抖振气动力合理建模为出发点,建立了基于状态空间方程的非定常、非线性时域抖振力模型。提出了能同时准确模拟非定常、非线性效应的纯时域气动力模型——缩阶微分方程抖振气动力模型。利用主动控制风洞试验技术进行桥梁节段模型抖振力荷载测量试验,对比研究了窄带和宽带谐波来流条件下的桥梁断面气动力荷载的非定常、非线性特性。

At present, Scanlan＇s linear quasi-steady formula is generally adopted as the model of the buffeting forces in the framework of buffeting theory, and the Davenport＇s concept of aerodynamic admittance is usually employed to modify the quasi-steady buffeting forces. Some present researches also indicate that the aerodynamic admittance varies remarkably with the turbulent characteristics and there is no uniform expression of aerodynamic admittance for the same bridge deck section. In addition, the study on nonlinear buffeting force is still in its infancy stage. Based on the above reasons, starting with the buffeting forces which are the key points of bridge buffeting analysis, the bridge deck section model buffeting tests are carried out utilizing actively-controlled wind tunnel test technique. The unsteady and nonlinear characteristics of aerodynamic forces are studied in two types of flow fields, i. e. , the narrow-band flow and the wide band flow. Finally, an aerodynamic buffeting model described by the reduced Nonlinear differential equation in time domain is proposed based on state space equations. The model can simulate the non linear aerodynamic effects and the frequency multiplication effects for different input amplitudes and frequencies.