Risk-based bridge scour management: A survey

Scour is a major cause of bridge failure and results in significant economic losses through disruption to operation. This phenomenon naturally affects bridges with underwater foundations and is exacerbated during high river and/or turbulent flows (e.g. due to extreme events). When scour reaches the bottom of or undermines shallow foundations, it may trigger various damage mechanisms that may influence the safety of the structure and force asset managers to reduce traffic capacity. Currently, assessing risk of scour is a heuristic process, heavily reliant on qualitative approaches and expert opinion (e.g. visual inspections). These types of assessments typically suffer from insufficient knowledge of influencing factors (e.g. hydraulic parameters) and the requirement to rely on several assumptions (e.g. assumed foundation depth). As a result, current scour assessment and bridge management practices do not provide reliable solutions for addressing the potential risk of bridge failures. In this paper, cross-cutting needs and challenges related to the development of decision support tools for scour-risk management are highlighted and some preliminary results of a literature survey are reported. The review has been performed with several objectives: (i) identifying scour-risk indicators describing hydrodynamic actions and the asset condition; (ii) defining indirect and direct consequences needed to assess the risks associated to different decision alternatives related to scour management; and (iii) identifying existing approaches to scour inspections and monitoring as support tools for informed decisions. The results of this survey will serve as a base for future research aimed to develop an informed decision support tool to manage scour risk at both the bridge and at the network level.