环境振动系统识别方法的比较分析

对土木工程结构在自然环境振动条件下系统识别的方法进行了评述 ,重点讨论与比较了频域识别的峰值法 (PP)和时域识别的随机子空间法 (SSI) .实例分析包括一 15层高的钢筋混凝土建筑和一座钢拱桥 .实践表明 ,PP方法简单、快捷、实用 ,但结构阻尼无法识别 ,且振型识别精度不高 ;SSI方法计算工作量大 ,费时 ,但识别质量较高 ,借助于稳定图 ,可以识别出PP方法无法识别的相邻空间振型 .实用中建议 ,在现场实验时用PP方法检查实测数据并初步识别结构的动力特性 ,随后再用SSI方法做进一步的细致分析 ,确保系统识别结果的正确性

Comparison of system identification methods using ambient vibration measurements

The paper is intended to compare system identification techniques for evaluating the dynamic characteristics of civil engineering structures from ambient vibration data. Two system identification techniques used are the frequency domain based peak picking (PP) method and the time domain based stochastic subspace identification (SSI) method. A 15 storey reinforced concrete shear core building and a steel girder arch bridge have been chosen as case verification. The results demonstrate that the PP method is simple and fast. However, the damping ratio and mode shapes are not guaranteed. The computational load of the SSI technique is significantly higher than the PP method, but the quality of the identification is also higher. The SSI technique with the help of stabilization diagram can detect closely spaced frequencies that are possibly missed with the PP method and provides a more reasonable modal shape in most cases. For real applications, it is suggested that the PP method could be used on site to verify the quality of the measurements and to have a quick look at the overall dynamic behaviour of the structure. Afterwards the advanced SSI technique can be applied to detail or to ensure the results.