“Pile It On!”

Are you struggling with designing piles for your deck, or cottage? Well, don’t be afraid to “Pile On” more work with how easy this tool makes designing pile foundations. The concept is simple, specify the geometry, pile type, and basic soil conditions of your site, and get a Revit file with an accurate pile design. This includes the options to change: (1) Building Footprint and Load (width, length, total load), (2) Pile Dimensions (radius, depth, material, cap height), and (3) Soil Conditions (friction angle, unit weight, lateral pressure coefficient). Just like that, you will receive a fully detailed Revit model, alongside cost, carbon footprint, stability and settlement estimates. The configurator tool uses the dynamo player interface to allow for simple use and implementation. The “teaser image” and outputs for a sample scenario can be seen below in Figures 1 to 3.

User-Guide:

1. Open the “3Units_AlessandroKerr_Module8.rvt” Revit file in Revit.
2. Then proceed to the “manage” tab in Revit and open “Dynamo”. Once Dynamo has opened, open “3Units_AlessandroKerr_Module8.dyn” and return to Revit.
3. Now click the “Dynamo Player” in the manage tab in Revit. You will see the file.
4. Press the play button, then you can edit the inputs with the “Edit inputs” button (See figure below and figure 3a)
5. Then, the outputs will be automatically updated in the dynamo player along with the Revit model in Revit.
6. Enjoy your pile foundation design alternatives!

Model Details

This section is focused on outlining the details of the model, for someone who is interested in how the model was developed or wants to make changes. For example, certain aspects (soil bearing equation, cost estimates, carbon estimates, soil type, etc.) are fixed in the models but could be changed, or added into the inputs, for future iterations.

The model begins by asking for a wide range of inputs, all of which are necessary to facilitate the material and soil bearing capacity calculations. This includes: structure length and width, pile radius, pile height, the cap height to length ratio, total building load, and material choice. For the soil, the unit weight, friction angle, and lateral earth pressure coefficient are all potential inputs (See Figure 4 and 5). If the soil characteristics are not specifically known, a local soil geotechnical report will include sample values that can be used. For the lateral earth pressure, use Figure 6 below, which requires the L/D (pile length/diameter) and friction angle.

The nodal logic will now be broken down into the key steps (See Figure 7):

(1) Material Compressive Strength Calculation: The first necessary step is taking the pile geometry and material choice and determining the maximum compressive strength that can be applied to it. This takes the material selection, then selects the proper cross-sectional area equation and compressive strength (psi). The area changes because steel piles are hollow and concrete/timber piles are solid. A fundamental equation is that Q = F/A, so by taking Q*A/144*1000 (psi to psf to kips), the kips of force (F) that the pile can handle based on the compressive strength is calculated (See Figure 8). The total load is then divided by the resistance per pile to see how many piles are required.

(2) Soil Bearing Capacity: The material capacity needs to be compared with the allowable soil bearing capacity (See Figure 9). The soil bearing capacity uses an equation based on sandy soils (the Coyle and Costello method, see Figure 10). It assumes a uniformly stratified soil, and a pile depth less than the critical depth (approximately 15*D). The total load is then divided by the resistance per pile to see how many piles are required.

(3) Pile Spacing and Limiting Factor: From here, the maximum of the number of piles required from the soil and material requirements is taken. The total perimeter is divided by the number of piles to get the spacing between each. The limiting factor is simply the calculation that returned the larger number of piles (soil or material), see Figure 11 below.

(4) Create Pile Caps: The pile caps were created first (the rectangular beams that connect above the piles and support the foundation of the structure). The midpoint of each line of the structure was used to create cuboids of the inputted length. For a typical concrete beam, the height is usually between L/8 and L/16, in this case I conservatively assumed the height of the beams was the unsupported length (L) divided by 12, but this can be changed as an input, see

(5) Create Piles: The piles were created using the previously calculated spacing. This was done by placing points and cylinders at the set spacing (See Figure 13 below).

(6) Cost Calculation: With the geometry completed, some useful evaluation metrics could be calculated. The cost was calculated by first selecting the cost index from the material input (See Figure 14). These values were estimated based on standard industry values in Michigan but could be updated based on local pricing.

With this, using the volume of concrete from the pile caps, the driving distance, material costs, and a set up charge the overall cost could be computed. This takes the volume of the pile caps, depth of piles, and the material depth times the relative linear or cubic foot values (Figure 15).

(7) Carbon Footprint Calculation: Similar to the cost calculation, this first takes the carbon footprint index which selects the pounds of CO2 per foot cubed. These values were estimated from online resources (Figure 16).

From here, the index was used in combination with the volume of the designed piles. By multiplying the pounds of CO2 per foot cubed by the volume, and adding the pile cap CO2 emissions, the total pounds of CO2 for the system could be determined (See Figure 17 below).

(8) Settlement and Stability Estimates: Lastly, estimates for settlement and stability were created which allows for quick comparison between alternatives. Settlement was created by using pile surface area as a proxy, or one over the surface area. Stability of pile groups is important when relying only on skin friction (which is the case here), so the ability for piles to act in a group depends on the radius and spacing between the piles (See Figure 18 below).

(9) Outputs

The outputs, which are displayed in the dynamo player output can be seen below in Figure 19:

Video Demo

Here is a quick video demo that demonstrates how a user could interact and benefit from the pile configurator tool.

Limitations and Next Steps

This configurator tool served as viable prototype. There are several aspects that could be expanded on in the future. Firstly, the tool could easily be used in a generative design context which could optimize the depth/radius for a given load in terms of cost. For more details on the generative design side of the process, my module 7 assignment can be seen. This is a limitation that could be resolved through additional generative design testing. Other aspects that could be included in future iterations would include a toggle for different soil types (clay, silt, sand), different pile resistance equations (other than Coyle and Costello), more customizable layout designs, material cost inputs, and material carbon inputs to name a few. Right now, the design tool is limited to sandy soils, fixed cost estimates, fixed emission estimates, fixed resistance equation, and rectangular foundations. Nonetheless, I think this MVP successfully demonstrated the viability of this concept, but it could be expanded on before widespread use.

Conclusion

In the end, the tool provides immense benefit to contractors and engineers who want a quick, but reliable estimate for the pile geometry and cost. The configurator tool uses the dynamo player interface to allow for simple use and implementation across a wide audience.