During extreme floods,the superstructures of railway bridges may be submerged and may experience damage such as slipping and overturning under the action of water load.Focusing on the common form of superstructure of simply supported girder railways bridge,this study employs computational fluid dynamics methods to investigate the influencing factors of water loads on superstructure,computational methods,and their application in the assessment of bridge flood resistance capabilities.The results indicate that the horizontal drag,vertical lift,and overturning moment acting on the bridge superstructure are mainly influenced by factors such as inundation ratio,proximity ratio,Froude number,cross-sectional form,and aspect ratio.Among them,the inundation ratio has the most significant impact,with each component force coefficient changing significantly as the superstructure transfers from partially submerged to fully submerged,while these coefficients remain unchanged once the inundation ratio exceeds 3.The proximity ratio increases the water loads when it is less than 4.The larger the Froude number,the smaller the water loads coefficient.Under fully submerged conditions,structures with a smaller aspect ratio experience greater water loads.Under the same conditions,box girders experience less drag and lift but greater moment than T-beams.Bridges located in rapidly flowing river sections generally fail by slipping in a partially submerged state,among which railway box girders have the best flood resistance performance while single-line T-beams have the worst.
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