Structural health monitoring of offshore structures using ambient excitation

Abstract

This work explores the role of ambient excitation and empirical modeling in detecting damage in offshore structures. Two simple models of an articulated offshore structure are excited with the output of a stochastic process conforming to the ambient Pierson–Moskowitz wave distribution. Because ambient excitation (hence the resulting response) is typically modeled as a narrow-band process, the resulting response is ‘practically’ low-dimensional allowing for phase space methods of analysis to be applied. Based on the structure's response to this excitation empirical phase space models are constructed. Structural response data from an undamaged structure are used to make predictions on the response of a damaged structure. As damage is incurred, the resulting prediction error increases. The result is a data-driven approach which can successfully detect a stiffness degradation in model offshore structures. This technique is demonstrated effective for diagnosing the presence, and in one of the examples the magnitude, of the degradation.