The major damage to bridges occurs due to scour of the bed materials around piers and abutments during severe floods. This study involves the experimental investigations of the various scour patterns forming around abutment models tested with and without collars as scour countermeasures. The experiments were conducted in a rectangular channel under clear-water scour conditions. In the first part of this study, 34 experiments were conducted with semi-circular end abutment models with and without a collar for a period of 3 hours. Collars of various sizes were placed at different elevations on the abutment models, and the scour reduction efficiencies of collars were investigated for the different flow depths. Based on the results of the experimental studies, the optimum locations of collars on the abutments, which result in minimum scour depth around the abutments, are obtained at the bed level and below the bed level depending on the flow intensity values. In the second part of this study, the effects of flow depth and abutment length on the temporal development of local scour at bridge abutments were studied. 20 experiments were performed without collars for a time period of 8 hours. It was observed that at the upstream of the abutment, the depth of the local scour increases rapidly within the first three hours of the experiment for the different flow depths.

Many river bridges fail or are seriously damaged due to excessive local scouring around piers and abutments. To protect a bridge from scour-induced failure, it should be designed properly against excessive scouring and its scour criticality should be checked regularly throughout the service life to take prompt action. The Federal Highway Administration of United States (FHWA) developed a program, HYRISK, as a basis for evaluation of existing scour failure risk of a bridge. It provides implementation of a risk-based model, which is used to calculate the annual risk of scour failure of a bridge or series of bridges in monetary values. A case study is carried out for a bridge crossing Fol Creek in Black Sea Region (close to Vakfikebir), for the illustration of this software. Besides, hydraulic analysis and scour depth computations of the bridge are carried out via HEC-RAS program. Also, a study is carried out to recommend scour countermeasures that can be applied to the aforementioned bridge.