Aashto Flexible Pavement Design Excel Spreadsheet -

Understanding the 1993 AASHTO Flexible Pavement Design Equation

cell until the left side of the equation equals the right side.

: Predicted total number of 18-kip equivalent single axle loads (ESALs) over the design life. ZRcap Z sub cap R

For immediate access, the Engineering Community offers a widely used spreadsheet for these calculations. Introduction to AASHTO Flexible Pavement Design aashto flexible pavement design excel spreadsheet

Comprehensive Guide to Using the AASHTO Flexible Pavement Design Excel Spreadsheet

| Layer | Material | a-coeff | m-coeff | Thickness (in) | SN Contribution | |-------|----------|---------|---------|----------------|-----------------| | Surface | Hot-Mix Asphalt | 0.44 | 1.0 | 4.0 | 1.76 | | Base | Crushed Aggregate | 0.14 | 1.0 | 8.0 | 1.12 | | Subbase | Gravel | 0.11 | 0.9 | 10.0 | 0.99 | | | - | - | - | 22.0 | 3.87 |

To ensure a cost-effective design, engineers solve this equation from the top down. The spreadsheet should check that the top layer protects the layer directly beneath it: Protects the base material. Base Layer ( D2cap D sub 2 ): Protects the subbase material. Subbase Layer ( D3cap D sub 3 ): Protects the subgrade soil. Subbase Layer ( D3cap D sub 3 ): Protects the subgrade soil

| Criterion | Rating (1-10) | |-----------|---------------| | Accuracy (vs. AASHTO nomograph) | 8.5 | | Ease of use (basic) | 7.0 | | Transparency | 9.5 | | Error checking | 4.0 | | Advanced features (seasonal, optimization) | 3.0 | | Suitability for final design | 5.5 | | Suitability for preliminary/screening | 9.0 |

(Design Traffic): Total expected 18,000-lb over the design period. ZRcap Z sub cap R

Set the target difference between the left and right sides of the AASHTO equation to zero by changing the SNcap S cap N Phase 2: Layer Thickness Optimization SNreqcap S cap N sub r e q end-sub 000-lb over the design period.

Where:

A well-designed Excel spreadsheet for pavement design requires inputting several critical parameters:

The primary goal of the spreadsheet is to find the , a value that represents the total required strength of the pavement layers to survive its intended design life. Because this equation is mathematically complex, engineers use Excel's Solver or Goal Seek functions to find the SN that makes the equation converge. The Design Workflow

Whether using a free or commercial spreadsheet, the following step-by-step methodology will guide you through the design process: