PileGPw is an interactive software program developed to provide the distribution of load and computation of axial deformation of the piles within a pile group. This program is based on the elastic analyses provided by Randolph and Wroth (see references) for single piles and a pile group under axial loads only.

PileGPw can analyze regularly or variably spaced piles in any group configuration as long as locations can be described by a coordinate system. The piles may be of variable diameters; however, all piles in the analysis must be of the same length. This program can provide the distribution of loads within a group with a rigid cap and also the distribution of load within a group utilizing a flexible pile cap. Pile caps other than rigid can be modeled by introducing individual pile-head settlements. This feature allows the presentation of individual pile-load differences caused by a rigid pile cap.

Elastic Analysis

PileGPw is based on elastic analyses developed by Randolph and Wroth and published in "An Analysis of the Vertical Deformation of Pile Groups" and "Analysis of Deformation of Vertically Loaded Piles". Both of these publications provide a flexible mathematical model that recognizes individual member-load distribution and related axial-load deformation for any configuration of a pile or pier group. The mathematical matrices are based upon a model that recognizes individual member load-supporting capacity in skin friction and its relationship to end bearing.

This platform can provide an excellent basis for interrelationship of skin friction and end bearing contribution as the profession gains more specific information about these two factors in pile or pier load support.

In addition to flexibility, the mathematical model allows the shear modulus of the supporting subsoils to be used as a prime variable in seeking a problem solution.

The Randolph and Wroth method of analysis for vertical deformation within pile groups uses the superposition of individual pile displacement fields. The analysis considers the average behavior down the pile shafts separately from that below the level of the pile bases.

The displacement fields are determined by means of developed, approximate, closed from solution for the problem of a single vertically loaded pile. The analysis may be applied to any general pile group, the only restriction being that all of the piles must be embedded to the same depth. The soil is modeled as an elastic material characterized by a shear modulus which is assumed to vary linearly with depth, and a Poisson's ratio, assumed constant. The basic analysis is dependent upon the selection of realistic values for moduli; for this reason, a guide to determination of moduli gathered from various sources has been included with this software.

The PileGPw program is organized to allow the determination of the load distribution within the group and the pile group settlement for a rigid pile cap requiring all piles to settle the same amount, or to model a flexible pile cap where individual pile loads are determined based upon user-input deflections of individual piles.


  • PileGPw is capable of analyzing up to 400 piles in either a random or regularly spaced group where piles can have different lateral dimensions but are assumed to all have the same length.
  • Pile location coordinates (x, y) can be automatically generated for piles in rectangular grids, staggered rows, or arranged in a circle. The generated pile data can be edited or customized by the user in a spreadsheet mode, or in a graphical layout mode by right-clicking individual piles.
  • This program has been designed to allow the user to mix individual pile properties and dimensions.
  • If a flexible pile cap is designed as structurally rigid, then the load distribution to corner, side and internal pile may change by a factor of 2 or more. Rigid pile caps tend to increase differential loads on piles within the group because pile and pile-cap interaction. PileGPw can be used to estimate the distribution of pile loading within pile groups designed with non-rigid (flexible) pile caps by specifying the deflections of the pile cap at each pile. As the pile cap is designed with increasing flexibility, the differential between the loads on individual piles decreases, thereby distributing the loading more uniformly within the group. This feature, which requires an estimate of potential pile-cap deflection at each pile based upon its structural design, can assist the structural engineer in designing pile-group foundations.
  • A closed form solution for the deformation analysis of single piles subjected to vertical loads is provided. The procedure is based on the methodology presented by Mark Randolph and C. Peter Wroth in their 1978 article in the ASCE Geotechnical Journal titled "Analysis of Deformation of Vertically Loaded Piles". The procedure, while approximate, allows the user to take into account the inhomogeneities of a site's subsurface conditions. This allows the user to rapidly determine estimates of pile deformation and indicates the relevant soil parameters which need to be measured.
  • The single pile may be modeled as friction only, end bearing only, or a combination, and the pile may include an enlarged base. Also, the manner in which the the soil modulus changes with depth (gradual or significant increase) can be varied by the user. A single pile may be evaluated under more than one axial load in one run.