Study On Flood Forces Of T-beam Bridge Superstructure

Bridge is the main part of Chinese transportation system and plays an important role in economic society.With the continuous increase of global temperature,the change of weather conditions is inevitable.The change of precipitation mode leads to frequent natural disasters,especially floods.As an important part of transportation,bridges are the key to lifeline engineering.For low-grade highways,due to the small clearance of the bridge,the flood will hit the beam with great probability,which will have a greater force on the superstructure of the bridge with subsequent destruction.At present,there is a lack of relevant provisions on the flood force of bridge superstructure in the code.Domestic scholars mainly focus on the study of flood force of bridge substructure.Therefore,it is of great engineering significance and value to study the force characteristics of bridge superstructure in the process of flood action,and put forward reasonable and effective calculation and correction formula of flood force.The main contents of this paper are as follows:(1)Two-dimensional and three-dimensional numerical flumes are established based on CFD software,and open channel flow is used to simulate the flood force.By comparing with the model test data of our research group,the numerical calculation model,meshing scheme and various parameters in software in this paper are verified,and the numerical calculation method for calculating the bridge flood force is established.(2)Through model test and numerical simulation,the influence of different factors(submergence rate,bottom boundary,in-flow velocity,the opening rate of the collision barrier,beam height-width ratio,transverse slope of bridge deck and entrapped air compression)on the flood force of T-beam bridge superstructure is studied,and the calculation method of water force coefficient is proposed.(3)The 1:20 scaled numerical simulation model of the bridge was built,considering the influence of the trapped air in the chamber formed by diaphragms.Based on which,the current force characteristics and flow field characteristics on the superstructure of simply supported T-beam bridge,as well as its failure mechanism,are investigated elaborately.Results show the solid crash barrier contributes as much as 31 % of the horizontal force,and the contribution of entrapped air to the vertical force is up to 18 %.The solid crash barrier and entrapped air is believed to be the critical factor of superstructure failure.