【作者】 郭震山；

【导师】 项海帆； 朱乐东；

【作者基本信息】 同济大学 ， 桥梁与隧道工程， 2006， 博士

【摘要】 气动导数是描述主梁断面气动性能的重要参数，在大跨度桥梁颤振和抖振分析过程中起着至关重要的作用。气动导数一般通过节段模型风洞试验获得。按照振动驱动机制不同，节段模型试验方法可分为自由振动法和强迫振动法两大类。与自由振动法相比，强迫振动法具有响应信号的信噪比大，气动导数识别结果离散度小，精度高，对应折减风速范围宽等优点。但由于所需试验设备复杂、一次性投资大等原因，强迫振动法一直没有得到深入的研究，目前还处于两自由度水平，识别理论还不完善，识别结果也不太理想。鉴于这种状况，本文从识别理论和试验技术两个方面对强迫振动法进行了深入的研究，主要内容如下： 开发研制了节段模型三自由度耦合强迫振动装置，该装置既可使节段模型沿竖向、侧向或扭转方向作可控的单自由度简谐强迫振动，又可沿任意两个或三个方向作可控的两自由度或三自由度耦合强迫振动。 将分状态强迫振动频域法从竖弯和扭转两个自由度的水平拓展到了竖弯、扭转和侧弯三个自由度的水平，首次实现了用三自由度分状态强迫振动频域法对18个气动导数的识别。提出了三自由度耦合状态强迫振动频域法。通过使节段模型沿竖向、侧向和扭转方向作不同频率的耦合振动，仅需一次试验就可获得所有18个气动导数。发现了节段模型实际强迫振动频率与预设频率之间的小量偏差是降低频域法识别精度的主要原因之一，为此对试验技术进行了相应的改进，在对超长预试验振动信号进行精确频率分析的基础上，对模型振动频率进行微调，达到有效降低上述频率偏差的目的，从而使频域法的气动导数识别精度得到了明显提高。 在对加速度时程信号进行数值积分求解速度和位移时程的问题上，提出了确定初始速度和初始位移的新方法，并集合样条函数积分、椭圆数字滤波，双向滤波技术等数字信号处理技术，建立了一个可以得到精确可靠的速度和位移时程信号的处理方法，避免了目前利用振动参数生成速度和位移信号所带来的误差。通过对动荷载成分的研究，提出了全新的高精度自激力时程获取方法，为建立完善的强迫振动时域气动导数识别方法奠定了基础。该方法摒弃了之前将特定风速与零风速下节段模型所受动荷载按对应相位简单相减得到自激力时更多还原

【Abstract】 As a kind of important parameters describing the aerodynamic properties of bridge decks, aerodynamic derivatives are essential and exert a great role in predicting the flutter and buffeting performances of long-span bridges. In practice, the aerodynamic derivatives are often obtained via wind-tunnel tests of sectional model. According to different driving ways of vibration, the sectional model test methods can be classified into two major categories, i.e. free-vibration method and forced-vibration method. Compared to the free-vibration method, the forced-vibration method is regarded to have the following advantages: low noise level, low spread and high precision of identified results, and wide range of reduced wind speed. However, the forced-vibration method still remains at 2-DOF level because of the complication and high cost of the relevant test equipments, and the identified results based on the current theory and testing technique are not satisfied. In this connection, both the identification theory and testing technique of forced-vibration method are investigated comprehensively in this study. The major contents of the research are as follows:A new 3-DOF forced-vibration device has been developed for the identification of aerodynamic derivatives of bridge decks. Using this device, the sectional model can be forced to make a controllable 1-DOF harmonic oscillation in any one of the vertical, lateral and torsional directions, or a controllable 2-DOF or 3-DOF coupled harmonic oscillation in any two or three directions.The current frequency-domain method of state-by-state forced-vibration for the identification of aerodynamic derivatives is extended from 2-DOF (vertical and torsional directions) to 3-DOF (vertical, lateral and torsional directions). All the 18 aerodynamic derivatives can then be identified using the extended method. A frequency-domain method of 3-DOF coupled forced-vibration is proposed for first time for the identification of aerodynamic derivatives. By setting different vibration frequencies for the vertical, lateral and torsional vibration components respectively,更多还原