GROUP is a well-accepted tool for analyzing the behavior of pile groups subjected to both axial and lateral loadings. The program was developed to compute the distribution of loads (vertical, lateral, and overturning moment up to three orthogonal axes) applied from any multiple locations in the pile cap to piles arranged in a group.

The program generates internally the nonlinear response of the soil, in the form of t-z and Q-w curves for axial loading, in the form of p-y curves for lateral loading and in the form of T-q curves for torsional loading. A solution requires iteration to accommodate the nonlinear response of each pile in the group model. Program GROUP solves the nonlinear response of each pile under combined loadings and assures compatibility of deformations and equilibrium of forces between the applied external loads and the reactions of each pile head.


Selected Features

p-y Curves

Various built-in p-y curves including:

  • Clay
    • Soft Clay (Matlock)
    • Reese Stiff Clay with or without free-water
    • API Soft Clay With User-defined J.
    • Modified Stiff Clay without free-water.
    • Modified soft clay with initial K
  • Sand
    • Liquified sand (Rollins).
    • Reese Sand
    • API O'Neil Sand
  • Elastic subgrade.
  • Silt (Cemented c-φ).
  • Reese Weak Rock.
  • Strong rock (Vuggy Limestone).
  • User-input p-y curves.
  • Elastic Subgrade.

Pile Sections

User defined piles with circular, rectangular, and wide-flange sections, with option to include nonlinear flexural stiffness for standard reinforced concrete sections for complex composite sections with structural streel inserts

  • Elastic
    • Circular (hollow or full)
    • Rectangular
    • Custom widge flange
    • Predefined AISC sections from built-in library
    • User defined sectional properties
  • Nonlinear
    • Circular section with or without rebar reinforcements
    • Circular sections with casing
    • Circular steel tubes
    • Predefined AISC sections from built-in library
    • Prestressed square sections
    • Presstressed octagonal sections
    • User defined EI


Consider combined loadings with load factors with ability to compute maximum and minimum envelops for load cases and load combinations.

Specify concentrated loads (at any position) at the pile cap and/or distributed lateral loads (using local or global axes) at the piles.

Option to use cyclic model for p-y curves where available.

Consider application of lateral loads.

Soil Movement

The user is able to input a profile of soil movements versus depth as additional loading on the pile. The movements of the soil may be produced from any action that causes soil movements, such as movements due to slope instability, lateral spreading during earthquakes, and seepage forces.


Option to to use multiple cores for considerable reduction in computing time on large models.

Consider push-over analysis.

Improved algorithms to improve solution accuracy and convergence in nonlinear problems.

Consider laterla soil resistance against embedded pile caps and optionally specify reduction factor on axial capacity of each individual pile.

Toggle computation of required unit side friction and top and bottom of each layer along with a unit tip resistance.

Compute the foundation stiffness matrix based on equivalent elastic stiffness.


Individual pile bending moment, shear force, mobilized sectional properties, or curvature of piles under each load case, and more are outputted for each example.

Optionally print out a text file (response file) with equivalent nonlinear springs along the pile, which is useful for performance of complete soil-structure interaction analyses using other structural software.

p-y curves may be automatically generated by the program and printed for review. Points of internally generated p-y curves can be requested for output according to user-defined levels of deflections.

Export loading, pile group layout, or graphs directly to MS-Excel.

Modeling and Model generation

Quickly create models from predefined templates using rectangular or circular pile groups.

Optionally import data from

or import pile layout and loading directly from MS-Excel files.

Consider up to 1000 vertical and/or battered piles in the same pile group analysis. Each pile can have different cross-section and flexural stiffness in orthogonal directions.

Boundary Conditions

Specify conditions pile-cap connection as
  • Fixed
  • Pinned
  • Elastically restrained with a user-defined rotational spring stiffness


GROUP comes equipped with electronic copies of detailed user's manual and a technical manual, as well as over 25 examples and input files. Download and view the examples and input files with GROUP running in Demo mode.