Modal parameter is the most important dynamic signatures for oil derrick structure. Using JJ160/ 41-K oil derrick structure as analytical models, free vibration decay signal of derrick structure under ambient excitation conditions was obtained by random decrement technique at first, then identification of modal parameters for impulse response signal under single and multiple stations was carried out by ITD method. Comparison and analysis of modal parameters were carried out by finite element analysis and frequency spectrum analysis. Numerical simulation analysis shows that the results of modal frequency identified by RD and ITD methods are almost consistent. However, the results of modal damping ratio identified have larger difference. Meanwhile, finite element analysis shows that the false damping ratio needs man-made discrimination because of noise disturbance. Is difficult to exert direct excitation on large oil derrick structures, so modal parameters identification carried out by RD and ITD methods is feasible. The article will provide effective reference for safety evaluation of oil derrick and prevent safety accidents in engineering.%模态参数作为石油井架结构重要的动力指纹,以JJ160/41—K型石油井架结构为研究对象,通过随机减量法获取环境随机激励下,井架结构的自由振动衰减信号,利用ITD法对单测点和多测点两种情况下的脉冲响应信号进行模态参数识别;并将有限元和频谱分析的模态参数进行对比分析.数值模拟分析表明,利用RD&ITD法识别的模态频率结果基本一致,而模态阻尼比的识别结果则相差较大,同时有限元分析表明,由于噪声的干扰,存在着虚假阻尼比,需要人为地进行甄别.故对于难以直接激励的大型石油井架结构来说,利用RD&ITD法进行系统模态参数识别是可行的,为做好井架结构的安全评估工作,减少工程事故隐患提供了有效的理论依据.
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