Falling-Weight Deflectometer Study: Optimizing the Number of Replicates and the Spacing of Test Stations

The Strategic Highway Research Program, managed by the Federal Highway Administration, includes a pavement evaluation component as part of its Long-Term Pavement Performance study. These evaluations include the use of falling-weight deflectometer FWD test devices. The purpose of this project was to determine whether the FWD test procedures could be modified to reduce cost, without losing a significant amount of information. Procedural changes could include a decrease in the number of test replicates andor an increase in the spacing between test stations. Variability between replicates was found to be relatively low a reduction in replicate drops from four to two would not cause a substantial loss in information. An increase in spacing between tests from 7.6 m 25 ft to 30.5 m 100 ft would result in a substantial loss of information. An increase in spacing from 7.6 m 25 ft to 15.2 m 50 ft would be reasonable if test section responses to FWD were to be summarized as expected values and dispersions. If extremes in pavement response e.g., miminum andor maximum stiffness were judged to be the most important results, the spacing between tests should not be increased from 7.6 m 25 ft.