Evaluation And Analysis Of Bridge Service Safety Under The Action Of Water Level Change

Based on the actual project,this paper explores the influence of water level change on the service safety performance of the bridge by using finite element analysis combined with theoretical calculation formula.Firstly,the influence of water level change on the flow velocity and velocity pressure of the river is discussed.Secondly,the influence of water level change on the scour action is explored.By establishing the finite element model based on the real bridge,the changes of stress,displacement and stability of bridge piers and main beams under various conditions were explored,and the evolution of internal stress of the bridge structure was analyzed before and after the change of water level.The findings:（1）Before and after the water level changes,the flow rate always maintains a strong linear relationship with the average depth of the water,and the flow rate presents a strong quadratic function relationship with the average depth of the water.At the same time,with the increase of the water level,the design flow rate increases the most.Compared with the general scour depth,the local scour depth is larger,but the general scour depth is greatly affected by the change of water level.Before and after the water level changes,there is a significant linear relationship between the water pressure and the pressure coefficient of the bridge pier.（2）The stress of the main beam is almost not affected by the change of water level.For the displacement of the main beam,the displacement in the X direction still increases to a certain extent along the positive X direction after the water level rises,while the Y direction and Z direction of each area of the main beam do not change much.After considering the scour action,it is obvious that the displacement of the main beam in the XYZ direction increases greatly.（3）It can be seen from the calculation results of the buckling coefficient that the change of water level will have a certain impact on the stability of the overall bridge,resulting in the development of the buckling coefficient in an unfavorable direction.After considering the scour effect,the stability of the bridge as a whole is greatly affected,and the buckling coefficient develops significantly in an unfavorable direction.（4）When the scour action is not considered,the pier stress is almost not affected by the change of water level;When scour action is considered,the stress of the pier increases to a certain extent with the rise of the water level.Compared with the condition without consideration of scour,the pier stress changes to a certain extent under the action of water level change,but the range of change is still small.（5）For the pier displacement,the displacement in the X direction and Z direction does not change much before and after the water level changes.When the scour action is not considered,the effect of water level change is more obvious for Y direction displacement.When scour action is considered,the effect of water level change is more obvious than that of displacement change when scour action is not considered.From the whole point of view,when the scour action is considered,the overall displacement of the pier is greatly improved.