# Pile Cap Design Example Using ASDIP FOUNDATION

March 11, 2020

ASDIP FOUNDATION is a structural engineering software for the design of concrete footings. It includes the design of pile caps based on the ACI 318 provisions and CRSI Design Guide. This document is a step-by-step pile cap design example using ASDIP FOUNDATION software.

As an example, consider the pile cap shown below, which supports a concrete column in a multistory building. The soils report recommends the use of 50-Ton allowable capacity 10" round piles. The column size is 26" x 26", and it's exposed to dead, live, and wind loads, whose reactions are shown below. Design the number of piles, the pile cap size, thickness and reinforcement.

## Pile Cap Design Steps

Enter the information given in the statement of the example, which are the loads and the materials. In this example the analysis of the structure provided the reactions per load case, as shown in the statement above. Note that all loads are applied at the top of the footing. The structure is subject to lateral wind loads and moments that will be transferred to the foundation. The At-a-Glance tab shows a summary of the design for a quick overview of your work as you go. The green check marks indicate that the checks passed.

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Enter the material properties, such as the concrete and reinforcing steel strengths, and the densities of concrete and soil cover. The soils report has provided the allowable pile capacity in compression as 50-Ton, and the lateral capacity of a vertical pile as 5 kips. Note that the service loads will be used to calculate the pile loads, and the program shows the controlling service load combination. The Condensed tab shows a more detailed set of calculations grouped by topic.

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ASDIP FOUNDATION calculates the pile cap dimensions based on standard pile group layouts. Enter the number of piles considering the calculated pile loads. In this example, we could use either 9 or 10 piles. For illustration purposes, let's use 10 piles with spacing of 3'-0" and edge distance of 1'-3", so the pile cap dimensions are 11.50 ft x 7.70 ft. The Detailed tab shows a complete set of calculations with exposed formulas and with references to the ACI code. An excellent tool for granular checking.

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ASDIP FOUNDATION calculates the axial load per pile, sorted by load combination. This information is used to check a number of limit states for one-way shear and punching shear. The first image below shows the calculated pile axial loads. The second image below shows the calculated one-way shear forces at the column face limit state. The third image below shows the calculated punching shear at a distance "d/2" and at the column face limit states. Note that all these results may be sorted by load combination, for granular checking.

The effective piles considered in the calculation are those falling inside the shaded light blue areas. ASDIP FOUNDATION considers an accidental pile offset in the calculations. In this example this accidental offset is 3 inches.

Enter the reinforcement information for the pile cap. Specify the concrete cover and the bar number and size. In this example we will use #8 rebars top and bottom in each direction. Note that the top rebars are not required for bending, but they will be required to comply with the minimum temperature and shrinkage reinforcement. ASDIP FOUNDATION generates a sketch of the pile cap in plan and elevation showing the rebars, similar to the construction drawings.

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## Takeaway

ASDIP FOUNDATION includes the design of pile caps, with multiple options to optimize the design easily. The design of pile caps may be cumbersome and error-prone, with multiple limit states checks. This pile cap design example shows that the task can be completed and optimized with ASDIP FOUNDATION within minutes.

For engineering background, please read the blog post Pile Caps - Structural Design Overview. For our collection of blog posts about foundation design please visit Structural Footing Design.