基于非线性振动响应瞬时特征的海洋平台结构多层次损伤识别方法研究

Damage identification is of great significance to ensure the safety of the offshore platform structures. Most of the existing damage identification methods are based on the linear vibration theory. However, the vibration responses of the offshore platform structures usually show nonlinearity in varying degrees, and most of the damages will aggravate the nonlinearity of the structures, which greatly increase the difficulty of the damage identification. The present research project focuses on the damage identification issue of the offshore platform structures based on the nonlinear vibration theory. First, the time-frequency analysis technologies of nonlinear and non-stationary vibration signals will be studied, which is intended to construct a new damage sensitivity index based on the instantaneous characteristics of the nonlinear vibration response. The new index can effectively eliminate the nonlinear interference from the structural system itself and realize the accurate detection and initial location of the structural damages. Based on this, a linear/nonlinear hybrid dynamic modeling method for the damaged structures will be developed. Then a system parameters identification method based on the instantaneous characteristics of the nonlinear vibration response and an adaptive solving algorithm will be proposed, which can achieve accurate location and assessment of the structural damages using incomplete excitation and response data. By using research approaches such as theoretical analysis, numerical simulation and physical experiment, the objective of the present research project is to develop a new method to identify the structural damages in multi levels based on the instantaneous characteristics of the nonlinear vibration response, and also to provide scientific basis and technical support for the structural health monitoring and safety assessment.

损伤识别对于保障海洋平台结构的安全服役具有重大的意义。目前现有的损伤识别方法大多基于线性振动理论，而实际海洋平台结构通常存在不同程度的非线性，且多数损伤的发生亦会加剧结构响应的非线性效应，这极大的增加了损伤识别的难度。本项目将基于非线性振动理论，研究海洋平台结构的损伤识别问题。发展非线性、非平稳振动信号的时频分析方法，构建一种基于非线性振动响应瞬时特征的损伤敏感性指标，排除结构自身的非线性对损伤识别的干扰，准确检测和初步定位结构的损伤；基于此，发展损伤结构的线性/非线性动力学混合建模方法，提出基于非线性振动响应瞬时特征的系统参数识别方法和自适应求解算法，利用非完备的激励和响应数据，实现结构损伤的准确定位和定量。借助于理论分析、数值模拟和物理模型实验等手段，本项目旨在发展基于非线性振动响应瞬时特征的结构损伤识别新方法，实现结构损伤的多层次识别，为海洋平台结构的健康监测提供科学依据和技术支持。

损伤识别对于保障海洋平台结构的安全服役具有重大的意义。现有的损伤识别方法大多基于线性振动理论，而实际海洋平台结构通常存在不同程度的非线性，且多数损伤的发生亦会加剧结构响应的非线性效应，极大的增加了损伤识别的难度。本项目基于非线性振动理论，研究了海洋平台结构的损伤识别问题。探讨了非线性、非平稳信号的时频分析方法，研究了损伤结构振动响应的非线性时频特性，发现结构的损伤会引起振动的瞬时频率和瞬时振幅出现波动以及非线性倍频现象，这些时频特征可用于结构非线性损伤的快速预警；提出了 “分段信号交叉相干函数法”和“短时时域相干函数法”两种非线性检测方法，并基于此构建了多个指标函数用于识别和定位结构的线性和非线性损伤；基于Volterra/Wiener模型的核函数构建了两种损伤判别指标，用于结构线性\非线性损伤的识别；针对损伤识别的“病态”求解问题，提出了一种迭代的总体最小二乘法，在高噪声、希测点的条件下，实现了对结构损伤的精细化识别；除此之外，研究了结构非线性损伤建模及非线性系统非参数化识别方法，为后续结构非线性损伤的深入研究奠定了理论基础。以上研究成果均进行了严格的理论推导、数值和物理模型实验验证，在结构健康监测领域产生了一些新的损伤识别方法，对于推动基于振动测试的结构健康监测技术在重大工程结构中的应用具有重大的科学意义，对于保障海洋油气资源的开发利用具有重要的理论意义和应用价值。