This synthesis reports on the state of the practice of falling weight deflectometer (FWD) usage as it involves state departments of transportation (DOTs) using these devices to measure pavement deflections in response to a stationary dynamic load, similar to a passing wheel load. The data obtained are used to evaluate the structural capacity of pavements for research, design, rehabilitation, and pavement management practices. It is anticipated that this synthesis will provide useful information to support guidelines, advancing the state of the practice for state DOTs and other FWD users, as well as equipment manufacturers and other involved in pavement research, design, rehabilitation, and management. Based on a survey conducted for this report, 45 state highway agencies (SHAs) reported using 82 FWDs, produced by 3 different manufacturers. The importance of FWDs among SHAs appears to be reflected in the survey results, as it was noted that SHAs conduct FWD tests on up to 24 100 lane-km (15,000 lane-miles) annually. Survey information presented in this report is supplemented by an extensive literature search, as well as communication with FWD calibration centers and FWD manufacturers. Individual SHA websites were also searched. Although current practice was limited to the United States, research published internationally was considered for historical context and for potential future research topics. A series of case studies share lessons learned from utilizing FWDs. (Author/publisher) This report may be accessed by Internet users at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_syn_381.pdf
Abstract