Model Study of Bridge Hydraulics, Edition 2

摘要

Most flood studies in the United States use the Army Corps of Engineers HEC-RAS (Hydrologic Engineering Centers River Analysis system) computer program. This study was carried out to compare results of heC-RAs bridge modeling with laboratory experiments. A laboratory flume was constructed specifically for this purpose. Nine experiments were performed for each bridge type for a range of flow and tailwater conditions. This report is the second edition. The first edition of the report considered the laboratory model to be distorted with 1:100 horizontal scale and 1:20 vertical scale. The second edition considers both distorted and undistorted interpretations of the laboratory models. Moreover, more advanced heC-RAs modeling techniques are used to better match the heC-RAs and the laboratory results. heC-RAs models were developed for the assumption of a distorted laboratory model and for the assumption of an undistorted laboratory model. The results were very close for the distorted and undistorted heC-RAs models. The maximum difference in computed water surface elevation was about 2 percent (0.28 ft in prototype dimensions) at the downstream bounding cross section. Overall, heC-RAs did very well in matching the laboratory results as long as the Froude number did not exceed 0.7 at the downstream bounding cross section. when the Froude number exceeded 0.7 at the downstream bounding cross section, the laboratory results still showed the effect of tailwater condition but the heC-RAs models did not.