United States Department of Transportation
i
Development of the Rolling Wheel Deflectometer (RWD)
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2020-03-17
[PDF-2.16 MB]
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Abstract:Nondestructive deflection testing has played an important role in pavement evaluation, design, and management for several decades. During this period, the tool of choice for structural evaluation has been the falling weight deflectometer (FWD), due to its ability to accurately measure very small pavement deflections by means of a nondestructive load generating impact and measurement with various types of deflection transducers. In terms of application, the FWD is overwhelmingly used for project-level evaluation and design. Over the last two decades, moving wheel deflectometers have been developed and tested to collect nondestructive deflection data from instrumented truck-trailer combinations traveling at normal highway speeds. Researchers have used various techniques to measure the surface deflections produced by the trailer’s loaded axle, with the purpose of measuring data with sufficient accuracy for network-level evaluation, such as pavement management activities. The Federal Highway Administration began funding Rolling Wheel Deflectometer (RWD) development in the late 1990s. This device consists of a 53-ft semi trailer with a dual-tire, 18-kip single axle that has been instrumented with several generations of deflection measuring systems, including a scanning laser, spot lasers, and most recently, machine vision cameras and custom-designed flashing strobe lights. The system has been developed and tested over the years to improve data accuracy, measurement of the full deflection basin, and applicability to pavement management. It has been demonstrated to over 20 State highway agencies as part of its deployment. One barrier to RWD data implementation has been its inherent differences from the current standard, as commonly used FWD data analysis techniques are not directly transferable to RWD data. This report discusses the differences in loading characteristics between devices, presents theoretical and field data comparisons, and provides strain correlations for use of both FWD and RWD data in network-level management. The field study included side-by-side FWD and RWD testing on 23 test sites in Mississippi.
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