HYDROLOGICAL ASPECTS OF BRIDGE DESIGN - CASE-STUDY

Many bridges are destroyed or fail completely during severe floods. If the cause of the damage is not a structural deficiency, it may be exc essive local scour around bridge piers and/or abutments. Although the mechanics of the local scour around these obstacles has been studied e xtensively, the studies investigating the hydrologic design aspects ar e limited in the literature. Insufficient hydrologic and hydraulic eva luations may result in uncertainties in bridge design. The optimum ret urn period for a flood hydrograph may be determined through a hydro-ec onomic analysis for bridge design. Lack of relevant hydrologic data, s uch as precipitation and runoff may lead to difficulties in obtaining the design parameters. Realistic judgment of the hydrologist on the lo cal hydrologic behavior of the project area is then required. In this paper, a case study performed for the hydrologic design of a bridge lo cated in a small basin subject to frequent floods is presented. Scour computations of the bridge have been performed for various combination s of runoff to check the foundation stability.