Numerical Investigation of the Performance of Caissons in Cohesive Soils under Cyclic Loading

Abstract

Cumulative plastic deformations under cyclic loading can be a key consideration in the design of caissons and short piles. In the case of caissons and piles serving as anchors for floating offshore structures, the possibility of loss of embedment due to upward ratcheting of the anchor under cyclic loading is a particular concern. This paper presents a finite-element investigation of a caisson subjected to cyclic lateral and inclined loading. A cyclic hardening model is employed to permit simulation of cumulative plastic deformations during loading below the ultimate load state. An asymmetric Fourier analysis was employed as a highly efficient alternative to a full three-dimensional analysis, and results using the two approaches were found to be in good agreement. A realistic range of material parameters was established through back-analysis of laboratory model tests published previously. Parametric studies were performed to assess the effects of small-strain soil stiffness, subyield stress–strain behavior, load inclination, soil–pile interface adhesion, and load reversals. Pile performance for cyclic loading with nonuniform load amplitudes was also investigated. The aforementioned factors were found to have a moderate to large influence on the magnitude of cumulative displacements under cyclic loading.