title: Dynamic response signatures of a scaled model platform for floating wind turbines in an ocean wave basin.
abstract: Understanding of dynamic behaviour of offshore wind floating substructures is extremely important in relation to design, operation, maintenance and management of floating wind farms. This paper presents assessment of nonlinear signatures of dynamic responses of a scaled tension-leg platform (TLP) in a wave tank exposed to different regular wave conditions and sea states characterized by the Bretschneider, the Pierson-Moskowitz and the JONSWAP spectra. Dynamic responses of the TLP were monitored at different locations using load cells, a camera-based motion recognition system and a laser Doppler vibrometer. The analysis of variability of the TLP responses and statistical quantification of their linearity or nonlinearity, as non-destructive means of structural monitoring from the output-only condition, remains a challenging problem. In this study, the delay vector variance (DVV) method is used to statistically study the degree of nonlinearity of measured response signals from a TLP. DVV is observed to create a marker estimating the degree to which a change in signal nonlinearity reflects real-time behaviour of the structure and also to establish the sensitivity of the instruments employed to these changes. The findings can be helpful in establishing monitoring strategies and control strategies for undesirable levels or types of dynamic response and can help to better estimate changes in system characteristics over the life cycle of the structure.
authors.affiliation: Hydraulics and Maritime Research Centre (HMRC), School of Engineering, University College Cork, Youngline Industrial Estate, Pouladuff Road, Cork, Ireland Dynamical Systems and Risk Laboratory, Civil and Environmental Engineering, School of Engineering, University College Cork, College Road, Cork, Ireland.
authors.forename: V
authors.initials: V
authors.lastname: Jaksic
authors.affiliation: Energy Engineering, School of Engineering, School of Engineering, University College Cork, College Road, Cork, Ireland Dynamical Systems and Risk Laboratory, Civil and Environmental Engineering, School of Engineering, University College Cork, College Road, Cork, Ireland.
authors.forename: R
authors.initials: R
authors.lastname: O'Shea
authors.affiliation: Dynamical Systems and Risk Laboratory, Civil and Environmental Engineering, School of Engineering, University College Cork, College Road, Cork, Ireland.
authors.forename: P
authors.initials: P
authors.lastname: Cahill
authors.affiliation: Hydraulics and Maritime Research Centre (HMRC), School of Engineering, University College Cork, Youngline Industrial Estate, Pouladuff Road, Cork, Ireland.
authors.forename: J
authors.initials: J
authors.lastname: Murphy
authors.affiliation: Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2BT, UK.
authors.forename: D P
authors.initials: DP
authors.lastname: Mandic
authors.affiliation: Dynamical Systems and Risk Laboratory, Civil and Environmental Engineering, School of Engineering, University College Cork, College Road, Cork, Ireland v.pakrashi@ucc.ie.
authors.forename: V
authors.initials: V
authors.lastname: Pakrashi
keywords: delay vector variance; offshore wind energy; signal nonlinearity; structural dynamics; tension-leg platform