ASDIP FOUNDATION is a structural engineering software for the design of concrete footings. It includes the analysis and design of pile foundations, based on the ACI 318 and AASHTO LRFD provisions. This document is a step-by-step AASHTO drilled pier analysis and design example using ASDIP FOUNDATION software.
AASHTO Drilled Pier Example
As an example, consider the 60" diameter concrete drilled pier, subject to the factored loads shown below. The soils report recommends a minimum length of 100 ft, and it has provided the soil properties for the different soil layers. Design the drilled pier reinforcement per the AASHTO LRFD 2020 provisions for Seismic Performance Zone SPZ 3.
AASHTO Drilled Pier Example Input
Go to the Geometry tab and enter the geometric dimensions of the pile. In this case, pile diameter is 60" and the pile length is 100 ft. The head condition is free. In this tab we can specify the longitudinal rebars and the cage length, as well as transverse rebars, either closed ties or spiral. In this example a spiral reinforcement will be used. Set the concrete clear cover as 3". All this information can be edited later to optimize the design.
Use the Materials tab to enter the pile material properties in the Pile tab, such as the concrete and steel strength. In this case f'c = 4 ksi and fy = 60 ksi. Go to the Soils tab to specify the material properties of the soil. The software allows to model up to 4 layers of soil, being the top layer the most critical. For each layer, enter the thickness, the sol type (either Clay of Sand), and the horizontal modulus of subgrade reaction. The soils report has provided these values as shown in the statement of the example.
Go to the Loads tab and enter the loads applied on top of the pile. Note that the given loads are already factored since they correspond to the Extreme Event I load combination including seismic, so we will enter these values as pre-combined loads in the program. Finally, click on the Show Parameters button to specify the seismic provisions. In this case the project is located in a Seismic Performance Zone SPZ 3, per AASHTO classification.
AASHTO Drilled Pier Example Output
With the input information ASDIP FOUNDATION will perform the lateral analysis of the pile, considering a series of non-linear springs to model the soil properties. Click on the Lateral Analysis tab in the right pane to see the analysis results in a tabular format, showing the shear, moment, and deflection at every 2 ft of pile length. Click on the Graph > V, M, D Diagrams tab to see this information graphically.
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 all checks passed. The Condensed tab shows a more complete set of results grouped by topic, great for a more detailed overview of your design. The Detailed tab shows a complete set of calculations with exposed formulas and with references to the AASHTO code. An excellent tool for granular checking.
In this example, the maximum forces along the pile are Pu = 700 kip, Vu = 60 kip, and Mu = 938 k-ft. Maximum service deflection is 0.19". With this information the program checks multiple code conditions to design the reinforcement. It is shown that 20 longitudinal rebars #10 comply with the minimum and maximum area of steel limitations by code. The minimum cage length requirement varies according to the SPZ. In this case, the reinforcement cage must extend the full pile length. The program checks the minimum transverse area of steel at different locations along the pile. In this case, a Spiral #6 @ 4" pitch x 70 ft at top and Spiral #6 @ 9" pitch x 40 ft at bottom comply with all the code provisions.
ASDIP FOUNDATION generates the interaction diagrams of the pile, and compares this capacity versus the applied loads, as show in the Graph > Interaction Diagram tab. The Construction tab shows the design sketches with the pile dimensions and reinforcement, similar to the construction drawings.
Takeaway
ASDIP FOUNDATION includes the analysis and design of drilled piers per AASHTO LRFD, with multiple options to optimize the design fast and easily. The design of concrete piles, such as Auger Cast Piles and Drilled Piers may be cumbersome and error prone. This example shows that the design can be completed and optimized in minutes using this software.
For our collection of blog posts about foundation design please visit Structural Footing Design.
Detailed information is available about this structural engineering software by visiting ASDIP FOUNDATION. You are invited to download the Free 15-day Software Trial, or go ahead and Place your Order.
Best regards,
Javier Encinas, PE
ASDIP Structural Software