Experimental and numerical study on the capacity of a winged monopile

Monopiles are widely used for offshore wind power foundations to mainly withstand the horizontal loads transferred from wave, current and wind. Although typically the soil strength increases with depth, close to the sea bed, the lateral capacity is often low. Instead of traditionally increasing the embedded depth, increasing the pile cross-section through 'wings' close to the pile head is an effective way to reduce the pile head deflection. This study performs a series of model tests and finite element analyses to investigate the effect of the wing geometry on the lateral response. Comparisons between the piles with and without wings show that the wings could significantly increase the lateral capacity. Further studies reveal that the profile of the capacity factors (normalized by the full cross-section of winged pile and soil strength) of the winged pile is approximately consistent with that of the wingless pile with a rough soil-pile interface adhesion. Finally, a formulation for the profile of the winged pile is proposed.