Abstract
This paper presents the effect of cyclic loading on the lateral behavior of monopiles in terms of load-displacement curves, deflection curves, andp-ycurves along the pile. A commercial software, Strain Wedge Model (SWM), was employed, simulating a 7.5 m in diameter and 60 m long steel monopile embedded into quartz sands. In order to account for the effect of cyclic loading, accumulated strains were calculated based on the results of drained cyclic triaxial compression tests, and the accumulated strains were combined with static strains representing input strains into the SWM. The input strains were estimated for different numbers of cycles ranging from 1 to 105and 3 different cyclic lateral loads (25%, 50%, and 75% of static capacity). The lateral displacement at pile head was found to increase with increasing number of cycles and increasing cyclic lateral loads. In order to model these deformations resulting from cyclic loading, the initial stiffness of thep-ycurves has to be significantly reduced.
Highlights
Monopiles have been frequently used to resist offshore environmental loads such as wind, wave, tidal, and ice loads
This paper investigates the lateral behavior of a monopile subjected to a lateral cyclic loading, focusing on the influences of the number of cycles and magnitude of cyclic lateral load
The static lateral capacity (Qu) of the monopile was calculated using the load-displacement curve at seabed from the Strain Wedge Model (SWM) analysis, and the cyclic lateral loads were chosen as 25%, 50%, and 75% of the static capacity
Summary
Monopiles have been frequently used to resist offshore environmental loads such as wind, wave, tidal, and ice loads. The offshore structure is known to undergo about 108 lateral cyclic loading events of varying amplitude [1] During this great number of cycles, the offshore structures need to endure fatigue, and surrounding soils should not alter much to satisfy the lateral capacity and displacement criteria. Engineering properties of surrounding soils can deteriorate because of a possible accumulation of excess pore water pressure induced by cyclic loading. The lateral displacement and rotation at pile head accumulate possibly leading to a serviceability problem This is believed to be considerable especially in the case of a one way cyclic loading. Instead of using complicated FEM, practical software analysing the lateral behavior of a pile by means of the Strain Wedge Model (SWM) was applied in [9] to quantify the deformation of an offshore wind turbine, illustrating an increase in the lateral displacement with increasing number of cycles. The loaddisplacement curves, deflection curves, and cyclic p-y curves were obtained from SWM; and the lateral behavior of the monopile was analyzed
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