ABSTRACT
The risk-based interrelationship between a hazard and its potential risk countermeasures needs to be handled interactively, not sequentially. For example, all bridges over water are generally assessed for scour vulnerability to develop a plan of action in case of flooding and to design appropriate countermeasures. Yanmaz and Apaydin (2012) discussed such methodologies for bridge scour risk Assessment and countermeasure design. The Federal Highway Administration developed a riskbased methodology and software named HYRISK (Pearson et al. 2002) to evaluate annual risk (R) of scour failure of an existing bridge in monetary values:
R K P C C CA= + +( )1 2 3 (8.1)
where rebuilding C1 is the cost of replacing the bridge as a result of a scour-induced failure C2 is the additional costs associated with vehicles running while detouring during the rebuilding
period C3 is the money loss of trucks and people in vehicles while detouring PA is the annual probability of scour failure K is a risk adjustment factor that can be obtained by
K K K= 1 2 (8.2)
where K1 is a bridge-type factor K2 is a foundation-type factor
A first estimation of annual probability of scour failure is obtained as a function of overtopping frequency and scour criticality. Scour vulnerability of a bridge can be assessed by the aid of the information about the nearby channel characteristics and substructure condition of the bridge concerned, and methodology such as the one developed by Yanmaz et al. (2007) can be used. Yanmaz and Apaydin (2012) describe the earlier methodology in detail and presented a case study for a bridge crossing Fol Creek in the Black Sea region of Turkey using this methodology to design a proper scour countermeasure using an economic analysis.
