Abstract: In order to guide the future design of new bridges or the assessment of existing ones,a multi-hazard de- sign framework is proposed on the basis of risk-consistent design for bridges under earthquake and scour hazards,and the appropriate scour depth considering the earthquake is investigated.Firstly,a fragility analysis considering scour is carried out for the bridge under earthquake to obtain the fragility surface and fragility curve of the bridge.Secondly,two probabilistic risk models respectively corresponding to earthquake and scour hazards are proposed and are used to reveal the relationship between the failure probability under seismic hazard and the scour depth and to obtain the joint failure probability of the bridge.Then,the scour depth corresponding to joint failure probability is taken as the appropriate scour depth to make a comparison with the designed value,from which load combination factors for bridge design are determined.Finally,a case study on a suspend bridge is carried out.The results show that the proposed method effectively considers both bridge risk and economy，so that it lays a foundation for explo- ring the combined action of earthquake and scour hazards for bridges with different types and scales.

Key words: bridge, risks, earthquakes, scour, multiple hazard