大跨度桥梁多模态耦合颤振二分法全自动搜索

在分析和评价国内外对大跨度桥梁风致颤振研究的成果和目前各种常用颤振分析方法优缺点的基础上,基于结构的固有模态坐标,进一步完善了大跨度桥梁多模态耦合颤振的双参数搜索状态空间法。通过将结构和气流作为一个动态系统,最后将颤振问题归结为数学上一个非对称实矩阵的广义特性值问题。在求解中,风速搜索采用了二分法加速收敛技术,频率采用搜索迭代法,该方法可以按指定的搜索精度,迅速搜索到颤振临界风速和颤振频率,无须设定步长,且能真实地给出各阶模态频率和阻尼比随风速的全过程。最后对具有理想平板截面的悬臂梁进行颤振分析验证了本文方法的正确性,同时对总跨度1177m的香港汀九大桥进行颤振分析,计算得到的颤振临界风速基本与风洞试验结果基本一致,进一步表明本文方法的可靠性和高效性。

FULLY AUTOMATIC ANALYSIS FOR MULTIMODE- COUPED FLUTTER OF LONG SPAN BRIDGES

Recent development of flutter analysis for long-span bridges is reviewed in this paper.Merits and drawbacks of the flutter analysis methods that are widely used at present are also pointed out.Based on the mode coordinates of the structure, improvement of the state-space method with double parameter searching for coupled flutter analysis of long-span bridges is presented.By combining the structure and the wind action into one system,the governing flutter equation of the system is converted into a generalized eigenvalue problem of an asymmetrical real matrix.A dichotomizing search method is adopted to search the critical flutter velocity an iteration searching method is employed for searching the critical flutter frequency.The proposed method can be employed to find the occurrence conditions of the fluttering state,especially,the process of the modal frequency and the damping-ratio variations with wind velocity.Finally,the flutter analysis of a cantilevered beam with idealized thin-plane section is provided to illustrate the validity of the proposed method,and a flutter analysis for the 1177m long Hong Kong TinKao cable-stayed bridge is also performed.The results indicate that the critical flutter wind velocities are consistent with the test results,proving that the proposed method is both reliable and efficient.