ABSTRACT
Scour phenomenon concerns all hydraulic structures i.e. all earthen (river banks, embankments) or civil works (bridge piers, abutments) located in a hydraulic environment (river bed, river flood plain, estuaries etc.). In France, for the only national highway network, more than 4000 bridges are concerned. Therefore, the General Direction of Infrastructures, Transports and Sea of the Ministry of Ecological and united Transition asked Cerema to write a methodology on risk-based analysis for civil-works structures located in scourable sites. This guideline (AROSA) is about to be published and fulfils the French technical instructions for civil-works surveillance (ITSOA). The methodology developed is based on risk approach i.e. it distinguishes hazard and its intensity in the one hand and vulnerability and its consequences (or issues) on the other hand. The risk is then defined as the combination of hazard cross vulnerability cross issues. To assess the risk of scour, the guideline suggests a 4 steps approaches (see extract on Figure 1) enabling firstly to identify scour sensitive works within a civil-works park (i), secondly applying a simplified risk-based analysis on these works (ii), thirdly applying a detailed risk analysis on more critical works (iii) and lastly proposing scour surveillance or countermeasures.
The purpose of this article is to present the AROSA methodology developed for scour risk-based analysis, the way scoring factors for scour hazard and vulnerability had been chosen and calibrated for the different steps. Then, the article will show a recent application of AROSA methodology on Paris suburban bridges.
