Effect of Scour on the Natural Frequency Responses of the Meteorological Mast in the Taiwan Strait

Wei-Chen Tseng, Yu-Shu Kuo, Kung-Chun Lu, Jing-Wen Chen, Chiou-Fong Chung and Ruey-Chyi Chen
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Wei-Chen Tseng: Department of Civil Engineering, National Cheng Kung University, Tainan 701, Taiwan
Yu-Shu Kuo: Department of Hydraulic and Ocean Engineering, National Cheng Kung University, Tainan 701, Taiwan
Kung-Chun Lu: Structure Control Division, National Center for Research on Earthquake Engineering, Taipei 106, Taiwan
Jing-Wen Chen: Department of Civil Engineering, National Cheng Kung University, Tainan 701, Taiwan
Chiou-Fong Chung: Taiwan Power Research Institute, Taiwan Power Company, Taipei 100, Taiwan
Ruey-Chyi Chen: Taiwan Power Research Institute, Taiwan Power Company, Taipei 100, Taiwan

Energies, 2018, vol. 11, issue 4, 1-18

Abstract: The meteorological mast (met mast) for the Taiwan Power Company’s offshore wind farm is located in Taiwan Strait near Changhua County. The p – y curve method recommended in the current offshore foundation design codes does not account for the local scour around the pile foundation; it overestimates the lateral pile deformation and underestimates the foundation stiffness. This paper presents a method to correct the initial modulus of subgrade reaction and modify the ultimate lateral resistance caused by the local scour. The natural frequency of the met mast structure is also determined by a numerical model and verified with the measured data in situ. A comprehensive parameter study is performed to analyze the effect of scour on the dynamic responses of the met mast. Two types of foundation model, a coupled-springs foundation model and a distributed-springs foundation model, are considered in the dynamic analysis of the met mast. The results demonstrate that using a distributed-springs foundation model provides a relatively accurate estimate of the natural frequencies of the met mast structure. Furthermore, the scour exerted significant effects on certain modes of the vibration responses. The natural frequencies of the met mast structure can be reduced by approximately 14% due to scour, particularly in the horizontal bending modes. This paper also provides a preliminary strategy for structural monitoring and analysis to detect scour damage on offshore wind turbines with monopile foundations.

Keywords: meteorological mast; monopile; scour; foundation stiffness; natural frequency (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
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