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South Dakota Department of Transportation
Project Synopsis
SD1992-06


Title: Effects of Increased Truck Tire Loads on Pavements
Project Researcher: Stuart Hudson,
Project Manager: Dan Strand
Research Period: -
Status:
Cost: $0.00

Problem Statement:Field observations indicate that an increasing number of truck owners are replacing dual tired wheel configurations with super single tires or singled-out-dual tires. Field observations also indicate that a growing number of truck owners are installing lift and/or tag axles equipped with minimum sized single tires to carry legal loads. These trends signify that more load is carried on each tire and the tire loads are approaching the legal maximum, 600 pounds per inch width of tire. This tire load level is nearly double the pounds per inch width of tire load caused by a typical, conventional dual tired wheel configuration. Therefore, within this problem statement, increased tire load is defined as carrying the same load on less tire width in configurations such as, super singles, singled-out duals, and lift and/or tag axles.

The increased tire load of super single tires or singled-out duals increases rutting in asphalt pavements and reduces fatigue life for all pavements. FHWAs Accelerated Loading Facility recently conducted tests on asphalt pavements which indicate that a super single tire causes twice the rutting and reduces the fatigue life by four times compared to dual tires under the same loading conditions. The effects of singled-out duals are expected to be even worse.

Factual data is not available to illustrate the extent which increased tire loading trend has developed or will continue to develop in South Dakota; nor is factual data available showing the extent to which South Dakotas highways are being impacted or will continue to be impacted by these trends. Research is needed to generate this factual data and quantify the extent which South Dakotas highways will be impacted.

Findings:

Research Objectives:
1  Develop a history of truck size and weight legislation.
2  Quantify the impact of increased tire loads relative to South Dakota's highways. Take seasonal effects into consideration.
3  Develop solution(s) which will reduce pavement damage due to increased tire loads.

Research Tasks:
1  Literature review. (a.)Summarize the evolution of the laws governing permissible loads. (b.)Summarize other relevant literature.
2  Study the traffic in various areas in South Dakota to determine the extent of increased tire loads.
3  Estimate the highway damage cost incurred because of increased tire loads.
4  Project the growth and highway damage cost if nothing is done to halt the use of increased tire loads.
5  Perform field tests on typical South Dakota pavements. Testing should be done under known tire configurations and loads, and seasonal effects should be taken into consideration.
6  Analyze the field data (strain, deflection, temperature, etc.) and apply it to a mechanistic model to project pavement life.
7  Develop solution(s) and estimate the costs for each. Consider using pounds per inch of tire width for any proposed changes that concern tire loads.
8  Submit a final report and an executive summary summarizing the literature, research methodology, data, findings, conclusions, and recommendations.
9  Present findings and conclusions to SDDOT Research Review Board upon completion of the project.

Documents Available:
SD1992_06_final_report.pdf

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