A simplified model for predicting the accumulated displacement of monopile under horizontal cyclic loadings

Monopile-supported offshore wind turbines are continuously subjected to stochastic cyclic loadings during its lifetime of 25-30 years and it is challenging to accurately predict the accumulated displacement of monopile. In this paper, a simplified model with two cyclic loading factors is proposed to predict the accumulated displace-ment of monopile in soft clay. These two cyclic loading factors could consider the effects of the pile diameter, number of cycles, loading profile and undrained shear strength profile on the accumulated displacement. The model is validated by comparing with the centrifuge data and results obtained from the hyperplastic accelerated ratcheting model. Furthermore, the evolution of the accumulated displacements of monopile for the ultimate limit state (ULS) storm loading history and the long-term fatigue limit state (FLS) loading history are also investigated. This paper could provide a method for design codes requiring an accurate estimation of monopile displacements.

Automated summary

A simplified model with two cyclic loading factors is proposed in this paper to predict the accumulated displacement of monopile in soft clay. The model is validated and found to have high accuracy through comparison with experimental data. In addition, the paper also investigates the accumulated displacement of monopile under different loading histories.