Determination of modal parameters is one of the most important steps in a maintenance strategy and/or structure health monitoring of aging fixed offshore jacket platforms during service life. This paper presents a new Ensemble Empirical Mode Decomposition-Hilbert transform (EEMD-HT)-based analysis to identify natural frequencies of the offshore structures under an artificial and natural excitation. An EMD processing algorithm is used to decompose the vibration response signal into a set of intrinsic mode functions (IMFs) and the EEMD is developed from the EMD to solve the vibration mode mixing in identifying the natural frequencies of the structure. In this study, the experiment of vibration response measurement was conducted on the actual offshore structure at site for both the artificial and natural excitations. A numerical model in an Eigen value analysis was also simulated to evaluate the consistency with the experiment. The main results demonstrate that the instantaneous (time-dependent) frequencies of fixed offshore jacket platform were successfully identified by the EEMD-HT technique under both the artificial and ambient excitation.

模态参数的确定是使用寿命期间固定老化海上固定平台的维护策略和/或结构健康状况监视中最重要的步骤之一。本文提出了一种新的基于整体经验模式分解-希尔伯特变换（EEMD-HT）的分析方法，用于识别人工和自然激励下的海上结构的固有频率。使用EMD处理算法将振动响应信号分解为一组固有模式函数（IMF），并从EMD中开发了EEMD，以解决振动模式混合以识别结构的固有频率。在这项研究中，振动响应测量的实验是在现场实际的人工和自然激励下进行的。还对本征值分析中的数值模型进行了仿真，以评估与实验的一致性。主要结果表明，在人工和环境激励下，EEMD-HT技术已成功地识别出固定海上平台的瞬时（随时间变化）频率。