Influence of Load Eccentricity and Aspect Ratio on Cyclic Response of Monopiles-Paper

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The study uses three-dimensional finite-element analysis to examine how load eccentricity and monopile aspect ratio affect the cyclic lateral response of monopiles in dense sand. The soil is modeled with the HSsmall constitutive model, which captures nonlinear stiffness degradation under cyclic loading. The numerical model is validated against centrifuge-test measurements.<br /><br />Across the configurations analyzed, increasing load eccentricity increases lateral displacement and rotation. The monopile’s rotation point moves upward as eccentricity increases, while the rotation angle rises approximately linearly. Increasing the embedment-to-diameter ratio (aspect ratio) reduces lateral displacement according to a power-law trend and reduces rotation exponentially. The normalized depth of the rotation point is largely unchanged by aspect ratio. Overall, aspect ratio has a stronger influence on deformation than load eccentricity.<br /><br />The calculated subgrade-reaction profiles along the shaft are relatively insensitive to either parameter, although the associated stiffness changes with displacement: greater embedment generally increases stiffness, while greater eccentricity reduces it. Shaft and base stresses are higher for smaller aspect ratios and larger eccentricities.<br /><br />The findings show that embedment and load application height are important design variables for controlling cyclic monopile deformation, and can inform more cost-effective monopile design.

Keywords

finite-element analysis

monopile

load eccentricity

aspect ratio

cyclic lateral response

dense sand

HSsmall model

lateral displacement

rotation angle

subgrade reaction