Highway bridges are vulnerable to extreme hazards such as earthquakes,scour,fire,and blast load.Current bridge design specifications deal with various extreme hazards independently and consider widely varying design level return period events for different hazards.Therefore,a risk-consistent multi-hazard bridge design framework is required to guide the design of new bridges or the retrofit of existing bridges.Scour and earthquakes are the most common causes of bridge collapses in the United States.This paper investigates the appropriate way to combine earthquakes and scour considering the simultaneous occurrence of these two hazards while also proposing a risk-based design approach to address scour and earthquake demands together.