Fuzzy-Monte Carlo simulation for the safety assessment of bridge piers in presence of scouring

Bridge scour is the removal of sediment (sand and rocks) around bridge abutments and piers due to the different river flow over the year. Approximately the 60% of collapses occurring to the of bridges is directly or indirectly associated to scour; this phenomenon is very important in the bridges safety assessment. The depth of scour depends on many factors: type and amount of bed/embanked material transported by the river flow, nature and occurrence of flood, accumulations of debris, constriction or realignment of flow due to the presence of the bridge, geometry and orientation of piers, etc. Under a design point of view, the depth of scour can be evaluated through theoretical models involving hydraulic parameters. However, many of these parameters (flow characteristics, sediments, structural and geotechnical factors, etc.) are affected by uncertainty; in the safety assessment of bridges, a deterministic approach to the problem cannot be adopted. A proper assessment of structural safety must be performed taking into account the uncertainties involved in the problem. The uncertainty can derive by randomness so as by incomplete and inaccurate datasets and the development of a fuzzy-probabilistic approach permits to take into account some uncertainty involved into the problem. This paper proposes and discusses a Fuzzy Monte Carlo Simulation (FMC) to approach the assessment of the bridge safety in presence of scouring. To verify the feasibility of the proposed approach the FMC will be applied to the safety assessment of a case study.