# Bridge Assessment under Earthquake and Flood-Induced Scour
## 5 Discussion  
The presence of local scour induced by flood events can heighten the vulnerability of bridges imposed by later loads, such as that caused by an earthquake. Conversely, bridge flexibility might increase and help reduce earthquake load. However, the design philosophy and criteria used in the project could influence the overall safety of the bridge in scenarios involving local scour caused by flood hazards. In the last decade, several bridges in Albania, similar to the bridge under study, have had their foundations with piles uncovered by several meters due to the increase in flood events and, therefore, the increase in the risk of local scour. This situation significantly affects the structural stability of the bridge by causing a loss of lateral support at the foundations. Therefore, assessing the performance of the bridge for different local scour depths resulting from various annual peak flow discharges is crucial.  
The results show that the fundamental periods of the bridge do not increase significantly with the scour depth, and this is due to the considerable stiffness of piles. The fragility curves of the study bridge for element and overall system levels, developed for multi-hazard scenarios, exhibit minor sensitivity to regional flood hazards. The bridge collapse is governed by the flexural failure of the bent (comprised of two columns each) due to seismic actions regardless of the local scour depths. A similar observation is also made by analyzing the graph of surface fragility and seismic curves. Also, the bridge is outfitted with elastomeric bearings, demonstrating reduced vulnerability to the harmful consequences of local scour. This is due to the damping characteristics and flexibility  
Figure 12: Seismic risk curves of bridge.  
inherent in elastomeric materials. Additionally, the elastomeric bearings allow for greater adaptability to variations in load and movement. However, the increase in the local scour depth increases the probability of unseating the bridge superstructure in strong seismic activity.  
The results are summarized as follows:  
* The multi-span simply supported concrete bridge comprising elastomeric bearings and stiff foundations has low sensitivity to flood hazards.
* The seismic risk of a scoured bridge can be reduced by increasing the stiffness and depth of the foundations.  
This study increases the attention of research communities and government agencies for the importance of studying bridges in areas prone to local scour induced by floods and earthquakes, which can be compounded by climate change. It will also serve as a basis for future research on implementing comprehensive bridge design that accounts for the potential impacts of earthquakes and changing climate conditions in multi-hazard scenarios, including the increased frequency and intensity of extreme weather events. Further research should focus on the impact of local scour induced by flood events on the seismic risk of these bridges (i.e., supported single or multi-span concrete bridges) and compare them with integral or continuous bridges. For the same type of bridge, the impact of foundation types on the bridge fragility will be of interest. It should also compare the components of the bridge that affect their functionality.  
Conceptualization, T.K. and J.C.M.; data curation, T.K., J.C.M. and N.-S.D.; formal analysis, T.K.; funding acquisition, T.K.; investigation, T.K.; methodology, T.K., J.C.M. and N.-S.D.; project administration, J.C.M.; resources, T.K.; software, T.K.; supervision, J.C.M.; validation, T.K.; visualization, T.K.; writing--original draft, T.K.; writing--review and editing, J.C.M., N.-S.D. and Y.X. All authors have read and agreed to the published version of the manuscript.  
The paper is supported by the Project to Attract Foreign Experts (G2023133018L) from the Ministry of Science and Technology of China.  
Not applicable.  
The data presented in this study are available upon request from the corresponding author.  
The authors declare no conflicts of interest.