A series of centrifuge model tests on a single model pile subjected to different gravities in saturated sand were carried out, to investigate the behaviours of slender piles subjected to lateral monotonic and cyclic loads. Both static and cyclic p–y curves of the piles are derived from the measured bending moments of the pile shaft. The computed results of the proposed hyperbolic p–y curves with a modified initial modulus of subgrade reaction are in good agreement with the test results. For the model pile under lateral cyclic loads, it is indicated that the accumulated horizontal displacement at the loaded position is approximately linear with the logarithm of number of cycles. The effect of loading frequency on cyclic behaviours of the present model pile in saturated sand without an accumulation of pore water pressure is limited. The cyclic degradation factor of saturated sand is significantly larger than that of dry sand, which is mainly caused by the oscillated pore water pressure under cyclic loading. A group of cyclic p–y curves related to the number of cycles and the cyclic soil reaction ratio are presented, and a corresponding analysis approach is proposed for engineering applications.

This paper, using the blade momentum theory combined with dynamic inflow correction and stall delay correction, analyses how periodic surge affect rotor aerodynamics of the NREL 5MW turbine operating at three different regions of its power curve. Results show that surge has the largest effects on rotor aerodynamics in region under rated wind speed while the smallest in region above that. Besides, oscillation amplitudes of rotor aerodynamic loads are in linear correlation with surge frequency and amplitude in most cases, except that rotor power and torque in region above rated wind speed is in linear correlation with the square of surge frequency. Results of this analysis would provide reference data for designs of floating wind turbine systems.