Program for Sustainable Pavement Engineering and Research

Those responsible for constructing and maintaining local roads systems know better than most the complexity of their pavements. The pavement structures often have multiple layers of various ages, thicknesses, stress levels, materials, conditions and past traffic impact.

These complexities can be a challenge for local public works agencies and county engineers in their efforts to estimate the structural capacities of in-service pavements and develop cost-effective strategies for managing their pavement systems.

To aid in those efforts, as part of an overarching research project, the Program for Sustainable Pavement Engineering & Research (PROSPER) developed a tool for engineers to use in their routine pavement analysis, design, and asset management. The Pavement Structural Analysis Tool (PSAT) has the added benefit of giving city and county engineers another means to better communicate with the public and elected officials regarding pavement needs.

The easy-to-use PSAT is a Microsoft Excel, macro, and Visual Basic for Applications (VBA)-based automation tool that is comprised of several consecutive subsections. In addition to the tool, the PROSPER project team led by PROSPER Director Halil Ceylan developed a user guide to aid in the tool’s use.

“The PSAT developed as part of this project is beneficial to Iowa county engineers responsible for pavement management,” said Ceylan, who is also a professor at Iowa State University. “It helps users make informed decisions about managing paved county roads, and this leads to an increase in the overall performance of the pavement network and improvements in pavement preservation and rehabilitation practices.”

The tool offers users the ability to predict critical pavement responses (maximum stresses, strains, and deflections), calculate equivalent thickness, compute current traffic load repetitions, detect fatigue and rutting failures, compute the structural number of each layer, determine damage, and estimate the remaining service life/remaining service interval.

It also allows the user to analyze two different pavement systems and one pavement system for multiple purposes, including a structural capacity comparison, traffic effect under different axle loads, modulus effect using different equivalent moduli, and structural capacity for one pavement system at a time.

The tool as currently developed can analyze three different pavement types: (1) asphalt concrete (AC) on a stabilized base, (2) AC on a granular base, and (3) AC on a stabilized base and granular base. It also analyzes up to 10 layers by using the equivalent layer theory, where multilayered pavement systems are converted into three-layered systems—an asphalt layer, a base layer, and a subgrade layer.

The team hopes to continue work on developing tools to aid agencies by developing a smartphone-based version of the tool, a similar tool for rigid (concrete) pavements, a structural overlay design tool, and a platform that integrates several tools that have been developed or are in development, among others.

To learn more about the PSAT, view the user guide, and download the tool, go to the project page.

For more information about the previously developed Iowa Pavement Analysis Techniques (IPAT) tool, go to the project page or read about it in a previous Technology News edition from winter 2022.