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Geomechanics and Engineering
  Volume 19, Number 1, September20 2019 , pages 79-91

Numerical analysis of offshore monopile during repetitive lateral loading
Song-Hun Chong, Ho-Sung Shin and Gye-Chun Cho

    Renewed interest in the long-term pile foundations has been driven by the increase in offshore wind turbine installation to generate renewable energy. A monopile subjected to repetitive loads experiences an evolution of displacements, pile rotation, and stress redistribution along the embedded portion of the pile. However, it is not fully understood how the embedded pile interacts with the surrounding soil elements based on different pile geometries. This study investigates the long-term soil response around offshore monopiles using finite element method. The semi-empirical numerical approach is adopted to account for the fundamental features of volumetric strain (terminal void ratio) and shear strain (shakedown and ratcheting), the strain accumulation rate, and stress obliquity. The model is tested with different strain boundary conditions and stress obliquity by relaxing four model parameters. The parametric study includes pile diameter, embedded length, and moment arm distance from the surface. Numerical results indicate that different pile geometries produce a distinct evolution of lateral displacement and stress. In particular, the repetitive lateral load increases the global lateral load resistance. Further analysis provides insight into the propagation of the shear localization from the pile tip to the ground surface.
Key Words
    long-term monopile foundation; semi-empirical numerical scheme; terminal void ratio; shakedown; displacement evolution; soil densification
Song-Hun Chong: Department of Civil Engineering, Sunchon National University, Republic of Korea

Ho-Sung Shin: Department of Civil and Environmental Engineering, University of Ulsan, Republic of Korea

Gye-Chun Cho: epartment of Civil and Environmental Engineering, Korean Advanced Institute for Science and Technology, Republic of Korea

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