Nonlinear Corrosion Evolution and Lateral Bearing Capacity Degradation of Steel Tubular Piles Under Marine Environment

In this study, the Weibull corrosion model and the Winkler subgrade model were combined to investigate the variation of nonlinear corrosion rates and the mechanical performance degradation characteristics of steel pipe piles under different protective layer lifetimes and soil stiffness gradients. A computational tool utilizing the finite difference method was employed to compare the distribution of pile deflection, bending moment, and shear force, and to study the changes in stiffness degradation and lateral bearing capacity behavior over time. Result indicates that the corrosion rate of steel piles gradually accelerates but declines after reaching a peak. Their stiffness also gradually weakens and stabilizes after a rapid loss of stiffness. Due to the increase in soil stiffness gradient, stress concentration in the shallow region of the pile body is continuously exacerbated, causing the location of the peak bending moment within the pile cap at the pile cap to shift significantly upward. It also increases the risk of bending moment concentration in the vicinity. When the soil stiffness gradient increases from 5.0 MN/m 4 to 10.0 MN/m 4 , the increase in shear force peak is 13.05%. Additionally, extending the service life of the coating can delay the onset of stiffness degradation but accelerates corrosion and stiffness loss in the later stages, with the overall loss remaining essentially unchanged. The findings of this study can offer a practical basis for optimizing offshore monopile design and corrosion protection by revealing the nonlinear impact of corrosion on stiffness and capacity.