Computationally Efficient Three-Dimensional Continuum-Based Model for Nonlinear Analysis of Laterally Loaded Piles

A computationally efficient continuum-based model is developed for obtaining the nonlinear response of pile foundations subjected to a static horizontal force and/or moment at the pile head. In the analysis, the soil is modeled using nonlinear elastic constitutive relationships expressed as power-law or hyperbolic equations; these relationships relate the induced shear strain in soil to the secant shear modulus. The soil displacements in the horizontal plane are expressed as products of separable functions maintaining compatibility with the horizontal pile movement, and the principle of virtual work is applied to obtain the governing differential equations describing pile and soil displacements under equilibrium. These differential equations are solved using the one-dimensional finite-difference method following an iterative algorithm. The soil resistance parameters associated with the pile-displacement differential equation capture the effect of soil nonlinearity because these parameters are related to the secant shear modulus at different points in the soil. The accuracy and computational efficiency of the present analysis are established by comparing the pile and soil responses with those obtained from equivalent three-dimensional finite-element analysis which used the same soil constitutive relationships. The present analysis framework is further validated against the results of two full-scale field pile-load tests. Furthermore, monopile responses obtained from the present analysis are compared with those of three-dimensional finite-element analyses in which the soil is modeled as an elastoplastic material. It is shown that, for the purpose of design against lateral loads, elastoplastic approaches are not necessary because the present nonlinear elastic analysis can produce sufficiently accurate pile and monopile responses.