Abstract: Indirect action of flow poses a risk to bridge safety as it results in scouring of structural elements, i.e. it changes the geometry of the initial design state and thereby subjects it to new loading conditions. Periodic inspections of riverbed and bridge structure under water establish the actual bridge condition and associated rating, recommendations for monitoring, maintenance and/or repair measures and time to next inspection. Estimation of scouring hazard for a particular bridge and riverbed stability assessment are based on morphodynamic analysis of the erosive capacity of flow on the bridge profile and adjacent watercourse section. This paper presents the results of specialist hydrographic surveys, morphodynamic analysis of the stability of riverbed and protection structures, and underwater visual inspections of structural bridge elements conducted by the Faculty of Civil Engineering Zagreb. For riverbed condition category ratings “good” and “poor”, examples from Croatia where for a particular category characteristic damage is established involving the need for maintenance or repair are singled out.

Keywords: Erosion, morphodynamic analysis, bridge, scour, underwater inspection, ADCP

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