Abstract Offshore structures usually are implemented in harsh environmental conditions which make the structures disposed to different failures. Negligible failures may lead to catastrophic ones. To prevent potential catastrophic failure, development of robust damage detection methods for offshore structures is necessary. Damages change structure's dynamic characteristics. Among different dynamic characteristics, modal frequencies and mode shapes are utilized more often. Due to various problems regarding damage detection methods for offshore structures such as sensor installation and data acquisition in water, damage detection methods using limited sensors seems very vital. In this paper, a novel method called Improved Modal Strain Energy Decomposition Method (IMSEDM) is developed to detect structural damage of jacket-type offshore platforms using a limited number of sensors just above the water. The proposed method has two main contributions. The first is simultaneous use of both modal frequencies and mode shapes which make damage detection more accurate. The second is decomposition of modal strain energy into axial and bending. IMSEDM locates damaged elements by considering the impacts of the damage on axial and bending modal strain energy. The method is evaluated using an experimental jacket type offshore platform. The results confirm that IMSEDM can effectively detect damages with incomplete data.

中文翻译：

---

基于水位以上传感器数据的海上平台损伤检测改进模态应变能量分解方法

摘要 海上结构物通常在恶劣的环境条件下实施，这使得结构物会受到不同的破坏。微不足道的故障可能会导致灾难性的故障。为了防止潜在的灾难性故障，有必要为海上结构开发稳健的损坏检测方法。损伤会改变结构的动力特性。在不同的动态特性中，模态频率和模态形状被更频繁地利用。由于海上结构的损伤检测方法存在各种问题，例如传感器安装和水中数据采集，使用有限传感器的损伤检测方法似乎非常重要。在本文中，开发了一种称为改进模态应变能量分解方法 (IMSEDM) 的新方法，用于使用仅在水面上方的有限数量的传感器来检测导管架式海上平台的结构损坏。所提出的方法有两个主要贡献。第一个是同时使用模态频率和模态振型，这使得损伤检测更加准确。二是将模态应变能分解为轴向和弯曲。IMSEDM 通过考虑损坏对轴向和弯曲模态应变能的影响来定位损坏的单元。该方法是使用实​​验导管架式海上平台进行评估的。结果证实 IMSEDM 可以有效地检测数据不完整的损坏。第一个是同时使用模态频率和模态振型，这使得损伤检测更加准确。二是将模态应变能分解为轴向和弯曲。IMSEDM 通过考虑损坏对轴向和弯曲模态应变能的影响来定位损坏的单元。该方法是使用实​​验导管架式海上平台进行评估的。结果证实 IMSEDM 可以有效地检测数据不完整的损坏。第一个是同时使用模态频率和模态振型，这使得损伤检测更加准确。二是将模态应变能分解为轴向和弯曲。IMSEDM 通过考虑损坏对轴向和弯曲模态应变能的影响来定位损坏的单元。该方法是使用实​​验导管架式海上平台进行评估的。结果证实 IMSEDM 可以有效地检测数据不完整的损坏。