LPILE 2015

(Last Updated On: December 22, 2017)

lpile 2015

LPILE is a special-purpose program based on rational procedures for analyzing a pile under lateral loading using the p-y method. LPILE solves the differential equation for a beam-column using nonlinear lateral load-transfer (p-y) curves. The program computes deflection, bending moment, shear force and soil response over the length of the pile.

As an option, components of the stiffness matrix at the pile head may be computed internally by LPILE so users can incorporate basic soil-structure interaction in their super-structure analyses. Another option from LPILE provides graphs of pile-head deflections for various pile lengths, to help users with optimum pile penetrations (for lateral response).

Nonlinear lateral load-transfer from the foundation to the soil is modeled using p-y curves generated internally using published recommendations for various types of soils. Special procedures are programmed for computing p-y curves for layered soils and for rocks. Alternatively, the user can enter manually any other externally generated ip-y curves.

Five types of pile-head boundary conditions may be selected, and the structural properties of the pile can vary as a function of depth. LPILE has analytical features to compute the nonlinear moment-curvature relationships and nominal moment capacity of a pile’s section based on specified pile dimensions and nonlinear material properties. Optionally, the user may enter nonlinear moment-curvature relationships to be used in place of the internally-generated values. LPILE provides several design recommendations for rebar arrangements in drilled shafts.

LPILE has been written as a 32-bit application that uses 64-bit precision in computations. The program produces plain-text input files and output reports. A number of graphs can be generated by the program and be saved in several graphics formats for inclusion in project reports. LPILEruns under all versions of Microsoft Windows© from Windows XP through Windows 7 (32 and 64 bit versions).


  • Boundary conditions and loading
    (Features for Non-LRFD Analyses)

    • Five sets of boundary conditions are available to model the pile head:
      • free head,
      • pinned head with sway,
      • fixed head with sway,
      • elastically-restrained without sway, or
      • elastically-restrained with sway.
    • Depending on the boundary conditions, pile-head loading may be applied as:
      • lateral load,
      • bending moment,
      • specified lateral displacement, or
      • specified pile-head rotation.
    • Up to 50 different load cases may be applied at the pile head in a single analytical run. This is a helpful feature for the quick observation of pile behavior for a specified range of external loads.
    • Users can specify any of the applied loads to be used for computations of pile-head deflection vs pile penetration to check critical pile length and produce efficient penetration designs.
    • A set of distributed lateral loading may be specified and may be applied anywhere along the length of the pile. Distributed loading may be constant or may vary linearly with depth.
    • LPILE Plus has the capability to perform push-over analyses and can study the pile behavior after the development of plastic hinges (yielding).

(Features for LRFD Analyses - All New in LPILE v6)

  • LPILE v6 introduces the capability of performing analyses for Load and Resistance Factor Design (LRFD).
  • Up to fifty load-case combinations may be defined with up to 100 unfactored loads grouped in 13 pre-defined load types.
  • Load-case combinations are defined by entering the load factors for each load type and the resistance factors for both flexure and shear. Optionally, the user may enter the load case combinations by reading external text files (previously created by the user).
  • Unfactored loads are defined for:
    • shear,
    • bending moment,
    • axial thrust force, and/or
    • distributed lateral load.
  • Load types for unfactored loads are:
    • dead load,
    • live,
    • earthquake,
    • impact,
    • wind,
    • water,
    • ice,
    • horizontal soil pressure,
    • live roof,
    • rain,
    • snow,
    • temperature and/or
    • two user-defined load types.
  • Factored loads are computed for each load-case combination by multiplying the appropriate load factor by the sum of loads of the same type. Summary reports of the computed load-case combinations are generated by the program.
  • Generation of Lateral Load-Transfer (p-y) Curves
    • Soil-resistance (p-y) curves can be internally generated by the program for the following soils:
      • soft clay,
      • stiff clay with or without free water,
      • sand (Reese et al),
      • sand (API Criteria),
      • cemented c-phi soils,
      • strong rock,
      • weak rock,
      • liquefiable sand,
      • stiff clay without free water using initial k,
      • Piedmont residual soil,
      • Loess silt, and
      • elastic subgrade.
    • Internally-generated p-y curves may be printed at any depth for reviews or reference.
    • Users may optionally input their own lateral load-transfer (p-y) curves for specified soil layers.
    • LPILE automatically adjusts p-y curves for soil-layering effects (for example, where there may be layers of sand and clay).
    • User-defined multipliers are provided to increase or to reduce the soil resistance (p-y) curves at any points along the length of the pile. This feature may be used in seismic conditions to reduce the response of liquefied layers or in closely-spaced piles, to account for "Group" effects.
    • Internal modification factors are implemented to model pile batter and sloping ground surfaces.
    • An user-specified curve may be used to model the additional shear resistance provided by the soil at the base of large-diameter drilled shafts and/or short piles.
    • LPILE has the capability of analyzing the behavior of piles subjected to the free-field soil movement in the lateral direction.
  • Structural Features
    • Linear interpolation of bending stiffness is possible for piles with varying cross sections.
    • The user may optionally ask the program to generate and take into account nonlinear values of flexural stiffness (EI). These values are generated internally by the program based on the following:
      • cracked/uncracked concrete behavior,
      • user-specified pile dimensions, and
      • nonlinear material properties.
    • Based on the input pile properties, the program can generate graphics of:
      • Flexural Stiffness (EI) versus Bending Moment (M)
      • Bending Moment (M) versus Curvature
      • Interaction Diagram
    • Four values (K22, K23, K32, and K33) of a typical 6x6 matrix for foundation stiffness may be generated by the program for a range of loading. These values can be used to model nonlinear foundation springs in the analysis of the superstructure.
    • Version 6 allows the user to define up to 10 sections with nonlinear bending properties. This permits the designer to cut off part of the reinforcing steel from the lower sections of a drilled shaft, as is common construction practice.
    • LPILE has the capability to perform push-over analyses and can study the pile behavior after the development of plastic hinges (yielding).
    • A new feature in Version 6 is the power to automatically generate bundled bar arrangement for 2-bar and 3-bar bundles.
    • Also new in Version 6 is the ability to offset the reinforcing steel from the centroid. This option was provided to allow analysis of drilled shafts where the reinforcement was placed (or accidentally moved) off-center.
  • Features for Optimization of Pile Designs
    • Several pile lengths may be automatically checked by the program in order to help the user produce a design with an optimum pile penetration. For this purpose, users can evaluate the curve of pile-head deflections versus pile length.
    • Curves of flexural stiffness versus bending moment and/or moment versus curvature are provided to review the adequacy of the pile's section. In addition, the user may also observe the interaction diagram of the modeled pile section.
    • The user may observe the nonlinear values of the foundation stiffness matrix.
  • Functional Features
    • Soil layer data structures and input screens are improved to help the user enter data conveniently with defaulted values provided. Hints and notes were also introduced on input windows to assist the user for data entry.
    • Over 100 error-checking messages have been provided, making it simpler for occasional users to run the program and/or to debug run-time errors of more experienced users.
    • The Graphics menu can produce quick displays of all results contained in the output file, including:
      • pile deflection versus depth,
      • bending moment versus depth,
      • shear versus depth, and
      • mobilized soil reaction versus depth.
    • A custom-control chart can be used to prepare various engineering plots in high quality for presentation and report.
    • The files of input data and output data are text based and may be directly accessed from within the LPILE program, employing the user's preferred text editor or word processor.
    • A well-documented Technical Manual is provided with relevant theoretical equations. The User's Manual includes a full description of all commands contained in the program menu, and example problems that are supplied for reference. The Technical and User's manuals are now distributed in electronic form with the LPILE program.
    • Standard Windows operations, such as dialog boxes, speed buttons, grid cells, clickable buttons, drop-down list of options, and pull-down menu choices are all incorporated in the LPILE program.

Ensoft LPile 2015

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