Publication Number: FHWA-SA-96-012
Date: January 1996

NHI Offers Pavement Deflection Analysis Course

Pavement deflection measurement and analysis are valuable tools that help pavement design engineers learn more about the properties of various pavements. To enhance pavement engineers' knowledge of automated deflection measurement and backcalculation, the National Highway Institute (NHI) offers a pavement deflection analysis course.

The pavement deflection analysis course is presented over a 4-day period and includes lecture and discussion, case studies, and workshops. The course is designed for highway engineers who have pavement design and analysis responsibilities. The course is scheduled upon request.

The course offers an introduction to deflection measurement and its uses, materials characterization, and the fundamentals of mechanistic-empirical pavement design. Emerging backcalculation processes and protocols for nondestructive testing and analysis developed under the Strategic Highway Research Program (SHRP) are highlighted. Special focus is placed on how to interpret deflection data obtained with the falling weight deflectometer (FWD), a device which is quickly becoming the industry standard. Backcalculation software programs will be demonstrated, and participants will be given real-world problems to solve in computer workshops using four popular backcalculation programs--MODULUS, MODCOMP, BOUSDEF, and EVERCALC*.

Participants will gain from the course a better understanding of the following concepts:

• Elastic modulus (how pavement deflects) and how it can be determined using nondestructive testing or other methods.
• Fundamentals of the backcalculation process and analysis methods.
• Factors that should be considered when selecting deflection-based devices, including which device is gaining more acceptance and why.
• Factors that can affect the deflection data, including SHRP's quality-control procedures for FWD load deflection data.
• Layered elastic backcalculation computer programs, including their uses, strengths and limitations; types and sources of error associated with the process, and techniques used to minimize these errors; effects of unusual field conditions on the accuracy of backcalculated layer moduli and how these conditions can be handled during analysis.

"This technology is not mainstream," says Joe Maestas, FHWA's technical coordinator for the pavement deflection analysis course. "It is very specialized and is still an evolving science but has much potential. By offering the pavement deflection analysis course, FHWA is trying to enhance the proficiency of this science and technology within the highway community and to illustrate its many applications."

The New York State Department of Transportation (DOT) recently purchased an FWD, says Don Arcari, associate soils engineer for the DOT. Arcari attended the pavement deflection analysis course with eight people from his section last August in New York.

"Learning the different methods to backcalculate the resilient modulus was very helpful; it's no easy task," says Arcari. He adds that after taking the course his staff was better prepared to use the FWD and to analyze the results on a recent design project.

"Part of my job is to analyze deflection data," says Bill King, pavement systems research engineer/supervisor for the Louisiana Department of Transportation, who attended the course in Mississippi last September. "The course helped me understand what backcalculation is all about." King says he found the computer workshop particularly useful in illustrating which software programs are available and what they can do.

The pavement deflection analysis course can be conducted on-site for requesting highway agencies or preferably at each of the four long-term pavement performance (LTPP) regional FWD calibration centers, which are maintained in cooperation with host State highway agencies. The centers offer calibration services for LTPP and highway agency pavement deflection measuring equipment. SHRP products such as the FWD and FWD data-quality assurance software are becoming key elements of the LTPP data collection effort.

Interested highway agencies can request the pavement deflection analysis course through NHI by calling Lynn Cadarr, course scheduler, at 703-235-0528. Classes are limited to 30 people (State and local highway agency fee is $5,500 for each course, and the private industry fee is $10,000). For more information about course content, call Pete Parsons, course coordinator, at 703-235-0529.

SHRP FWD Calibration Center Contacts

Back to Articles in this Issue