Pile Foundations Analysis

The program computes the axial load, shear force and bending moment carried by each individual vertical or batter pile in a piles group foundation when subjected to a vertical load, bending moment and horizontal load, based on the Hrennikoff approach.

The following assumptions have been made:
a) The pile cap is infinitely rigid and rotates about the mass center of the piles group.
b) The origin of the coordinate axes is always located at the point of application of the vertical load.
c) The load carried by each pile is proportional to the displacement of the pile head.
d) The problem is two-dimensional, that is, all the pile movements take place in the same plane.

The structure is first modeled in the plane, defining pile lines containing one or more piles with the same coordinate and batter. The sign convention for loads, coordinates, and batter is positive as shown in the figure below.

Input Data

The required input data includes the acting service loads applied at the piles top level, and the pile properties such as diameter, inertia, axial stiffness, and modulus of elasticity. The program also allows modeling the piles as fixed or pinned at top, and analyzes the foundation either in sand or clay.

In addition, a tabular format is required for each pile line: an identification (numbers or letters), the number of piles in that line, the X-coordinate of the pile tops with the origin at the point of application of the vertical load, and the batter, if any, as the angle in degrees with the positive X-axis. The figure to the right shows the required input data.

Example

As an example, consider the piles group foundation shown at left and subjected to a vertical load of 113.1 kips, a bending moment of 173.4 k-ft, and a horizontal load of 39.4 kips.

Find out the forces in each individual pile.

Output

Once the data is entered, choose the Solve option from the Design menu.

The program will automatically calculate the axial, shear and bending forces taken by each pile. The output forces and displacements given by the program may then be used to evaluate if the applied loads are resisted by the foundation, according to the pile capacity given in the soil report.

Figure to the right shows the template related to this program with the example data.