EVALUATION OF THE STRUCTURAL BEHAVIOR OF TYPICAL HIGHWAY INLET GRATES, WITH RECOMMENDED STRUCTURAL DESIGN CRITERIA

This research study involved the load testing and structural analysis of eight typical State Highway Department inlet grates; six roadway and two median grates. Oher grate variables were: steel or cast iron, shape of grate members, and flat or sloped installed grate surface. The objectives of the study were: (1) to determine the structural behavior of the selected grates under static and dynamic wheel loads, (2) to develop criteria for designing inlet grates on the basis of structural strength and behavior, and (3) to make recommendations for possible revision of Federal Specificat RR-F-621b (dated 9/14/67), "Frames, Covers, Gratings, Steps, Sump and Catch Basin, Manhole", which may be used for acceptance of inlet grates. The inlet grates were subjected to incremental static wheel loads up to 10,000 pounds and 6000-pound rolling and impact dynamic wheel loads. Each grate was also subjected to flat plate load tests to determine the ultimate load capacity and mode of failure. Computer analyses were made to determine whether the behavior of the subject grates under static wheel loads could be predicted. This report contains the results of the static and dynamic loading tests, and recommended criteria for the structural design of inlet grates.