Investigation of location and severity of damage in four-legged offshore wind turbine stencil infrastructure by improved modal strain energy method

Subject Areas : Analysis of Structure and Earthquake

Seyed Reza Samaei ¹ (معاون فنی و امور زیربنایی ستاد توسعه سواحل مکران)
Madjid Ghodsi Hassanabad ² (Assistant professor, Department of Marine industries, Science and Research Branch, Islamic Azad University, Tehran, Iran)
mohammad asadian ghahfarrokhi ³ (Department of Marine industries, Science and Research Branch, Islamic Azad University, Tehran, Iran)
mohammad javad ketabdari ⁴ (Department of Marine Technology, Amirkabir University of Technology, Tehran, Iran)

Received: 2020-09-02 Accepted : 2020-12-13 Published : 2021-01-16

Keywords: Health monitoring, Splash zone, Modal strain energy (MSE), Offshore structure, Jacket,

Abstract :

Truss structures are among the most common offshore structures that are exposed to various damages during their service life. Unlike onshore structures, these structures are constantly exposed to waves, corrosion and damage to members, especially in their deck and splash zone. At shallow water depths, these structures are commonly used as the main structures for offshore wind turbines. After a significant period of life time of these turbines in the world, monitoring their structural health has become necessary. In this study, considering the difference between onshore and offshore structures that are exposed to periodic loads of waves and high seawater corrosion, improved modal strain energy method was used. In this method, the natural frequencies for detecting and quantifying the possible damages in deck and splash zone elements, which are more prone to damage, were considered. The results presented that the improved modal strain energy method had a higher accuracy in locating the damage than the original method (Stubbs index). Also, single and multiple damages, with low and high intensity, were determined with appropriate accuracy by this method.