Response of Piles with Wings to Monotonic and Cyclic Lateral Loading in Sand

Piles are required to withstand large lateral loads compared with the imposed vertical loads in certain applications in the offshore environment, such as for foundations for offshore wind turbines or as anchors for floating facilities. Although typically the soil strength increases with depth, close to the sea bed, the lateral capacity is often low. The requirement to limit pile head deflections necessitates the design of relatively long piles. Increasing the effective pile cross-section through "wings" close to the pile head is shown here with centrifuge model tests to reduce pile head deflections by approximately 50% compared with regular monopiles without "wings" for the same load level. The stiffer initial response of the winged pile also leads to smaller pile head deflections under cyclic loading, although the relative rate of accumulation is similar to that of a monopile. Simple methods for extrapolating from the monotonic pile head deflection to the deflection after thousands of cycles are compared with the results, and are shown to work equally well for piles with and without "wings".