ICT researchers strive to facilitate the development and timely implementation of cost-effective technologies that improve safety, durability, and reliability; reduce congestion and environmental impact; optimize the life and use of the transportation infrastructure; and maximize the return on taxpayer dollars.
Currently, two major research projects investigating the benefits of using wide-base tires are in the final stages of completion. The first, “Influence of Tire Parameters on Roadway Structures,” is a three-year study funded by Michelin Americas Research and Development Corporation and aimed at determining the effect of tire parameters on loading and damage. The second, “The Impact of Wide Base Tires on Pavements: A National Study,” is a five-year Federal Highway Administration–funded project that compares new-generation wide-base tires with dual-tire assemblies and provides recommendations about the use of the former.
Semi-trailer trucks with 18 wheels are a common sight on American interstates, but in the next few decades, they could be a relic of the past. Instead, semi-trailers with ten wider tires may be rolling along the interstates. The U.S. EPA’s SmartWay Transport Project promotes the use of wide-base tires as a way to improve fuel economy by reducing weight, aerodynamic drag, and rolling resistance.
ICT collaborated with Michelin Americas Research and Development Corporation to investigate the effects of existing and new wide-base tire designs on pavement performance. Evidence increasingly shows that the type and configuration of tires have significant effects on pavement performance. A model was developed to demonstrate the structural and environmental impacts of new tire designs.
Most existing pavement design methods assume that tire–pavement contact stresses are uniformly distributed over a circular area in the vertical direction only. However, actual tire–pavement surface contact stresses are nonuniform—they exist in three principal directions. The ignored stress parts, transverse and longitudinal stresses, highly impact pavement performance. The transverse component of these stresses is linked to important distresses of asphalt concrete pavement, such as surface cracking and near-surface cracking, while longitudinal stresses are associated with intersection shoving and cracking and layer interface slippage and debonding. This study has resulted in a comprehensive evaluation of existing assumptions embraced by pavement engineers about tire—pavement interaction and the impact of such assumptions on pavement analysis and design. Models of tires and pavement structures were developed to determine the nonuniform stresses and provide a more accurate prediction of pavement damage. The new approach examines bulk failure and is not limited to failures resulting from exceeding a strain threshold at a specific point.
At the same time, ICT researchers led a $1.2 million FHWA project to model and validate the use and effects of wide-base tires as an alternative to the conventional dual-tire system. The main objective of the study was to use advanced 3D pavement models to quantify pavement damage caused by contact stresses and to predict field performance.
Using theoretical modeling validated by testing on instrumented, full-scale pavements, the research team determined the relationship between tire characteristics and pavement damage. A prediction tool, known as ICT-Wide, was also developed based on artificial neural networks to obtain critical pavement responses that can be used for predicting pavement performance and service life.
A finite element approach, considering variables usually omitted in the conventional analysis of flexible pavement was utilized for modeling. More than 500 cases combining layer thickness, material properties, tire load, tire inflation pressure, and pavement type (thick and thin) were analyzed to obtained critical pavement responses. In addition, environmental impacts were determined using the life-cycle assessment (LCA) method; based on the bottom-up fatigue cracking, permanent deformation, and international roughness index, the life-cycle energy consumption, cost, and green-house gas (GHG) emissions were estimated. The methods developed in this study will allow engineers and agencies to assess the impact of wide-base and dual on the pavement network and analyze the economic and environmental effects of using those tires in relation to their impact on pavement performance.
“To make the outcome of this research effort useful for state departments of transportation and practitioners, a modification to AASHTOWare is proposed to account for the new generation of wide-base tires. The revision is based on two adjustment factors, one accounting for the discrepancy between the current mechanistic approach (AASHTOware) and the finite element model of this study, and the other adjustment factor addressing the impact of the new generation of wide-base tires,” says Professor Imad Al-Qadi, who having been studying the impact of wide-base tires for the past two decades, led this research on behalf of ICT.
In addition to modeling and pavement instrumentation for measuring pavement response to various types of tires, both projects address the sustainability and environmental effects of using wide-base tires. The research team leading these revolutionary studies at ICT predict that a decade after the projects are completed, wide-base tires will be increasingly seen on our highways.
Posted March 24, 2016