Instrumentation of an Offshore Nautical Radar and platform with a sensor suite for measuring vibrations in situ

Instrumentation of an Offshore Nautical Radar and platform with a sensor suite for measuring vibrations in situ

Poirazis, Christos (TU Delft Mechanical, Maritime and Materials Engineering)

Cicirello, A. (mentor)

Delft University of Technology

Offshore and Dredging Engineering

2023-07-24

Offshore nautical radar systems are exposed to harsh environmental conditions during their service life. The structure is subjected in return to multiple random vibrations. Assessing the impact that these vibrations have on the structural integrity of the radar is necessary for creating a concrete operation and maintenance plan, that can enable the avoidance of structural damage due to fatigue. The development of a sensor network for the long term monitoring of such vibrations can provide an insight into the structural behaviour of a structure and predict possible damage scenarios.

The objective of this thesis is to determine how to instrument an offshore nautical radar in order to monitor vibrations in operating conditions. To achieve such a feat, short term vibration measurements (for non-opearating conditions) are performed on a 5.7-meter-long radar antenna that is supported by truss tower (or mast) with a height of 20 meters, located in Rijkswaterstaat’s test site in Stellendam. The aim of this approach is initially to extract the modal properties of the two structures, examine their interaction, and gather relevant information that can facilitate the determination of what a future sensor network, for the long term monitoring of the antenna, could look like.

For the realization of such measurements two main system identification techniques are used along with a small sensor suite of accelerometers. Experimental Modal Analysis (EMA) is performed on the radar antenna, by approximating a laboratory setting with minimal environmental interference. The system’s dynamic properties are extracted and analyzed critically in order to identify suitable sensor specifications and fitting sensor positioning among others. On the other hand, an Operational Modal Analysis (OMA) is executed on the truss tower in an attempt to see how its structural behaviour may affect the radar antenna’s response and any future monitoring plan.

The results obtained from the aforementioned modal analyses, are employed to propose a long term sensor network for the radar antenna, along with monitoring techniques that can be used to achieve the goal of damage detection. What becomes also evident from the current approach, is the need of a better equipped sensor suite and a cross-validating Finite Element model, in order to achieve more robust results.

http://resolver.tudelft.nl/uuid:395dd29b-c8b4-4e38-8a88-8b1cae881141

Student theses

master thesis

© 2023 Christos Poirazis