Analysis Of Tsunami Load On Superstructure Of Coastal Bridge With Small Box Girders Under Broken Solitary Wave

Since the twentieth century,there have been many large-scale tsunamis around the world’s earthquake belt,affecting people’s production and life and coastal infrastructure to varying degrees.With the huge strategic demand of coastal bridge construction during the 14 th Five-Year Plan period and the construction needs of the “One Belt,One Road” initiative,the coastal bridges and overseas aided bridges are located in harsh marine environments.The tsunami will cause serious damage to the bridges and affect people’s production and life.However,the research on bridge tsunami force around the world is not perfect,and there are relatively few provisions and norms for calculation of tsunami load.Therefore,systematic research on the characteristics and mechanism of the bridge superstructure under the action of the tsunami has important theoretical and practical significance.The main content of this article is as follows:(1)Using ANSYS Fluent software,based on Goring algorithm and dynamic mesh method,a three-dimensional numerical simulation flume capable of simulating breaking surges is established.And the accuracy of the numerical wave making and the calculation accuracy of the tsunami load of the three-dimensional numerical flume are verified.It is proved that the numerical flume can accurately simulate the deformation and breaking of solitary waves on the slope.(2)The small box girder is the research object of the article which is commonly used in practical coastal engineering in China.The time history curves feature of horizontal force and vertical force of the broken surge load on the small box girder are analyzed.Through the division of each panel of the small box girder,the force characteristics and mechanism of important characteristic moments are studied.The results show that the horizontal force on the small box girder is mainly provided by the pressure on the front surface,the positive vertical force is mainly affected by the chamber pressure and the pressure on the front surface,and the negative value of the vertical force is mainly provided by the weight of the water on the roof.(3)Carry out three-dimensional numerical simulation calculation on small box girder models with different wave heights,clearance,water depths and horizontal positions.Combining the characteristics of the flow field and the mechanism of the tsunami force.Various factors of the peak horizontal force and the peak vertical force of the beam tsunami are studied respectively.The results show that the tsunami force increases with the increase of the wave height,and the wave height is one of the most important factors affecting the tsunami force;as the clearance increases,the tsunami force decreases;when the initial water depth is larger,the tsunami force increases;and with the distance from the top of the slope changes.The flow field is different,and the characteristics of the tsunami force will change.(4)Through the 1/40 scale model test carried out in the laboratory of Southwest Jiaotong University,a series of water flume tests were carried out to study the time history characteristics of the horizontal force and vertical force of the broken solitary wave on the small box girder are studied,and the variation of the tsunami load peak with the wave height,clearance,and water depth are studied.The results show that the time history of horizontal force is a continuous positive impact,and the time history of vertical force presents a trend of positive first and then negative.The tsunami force increases with the increase of wave height,and decreases with the increase of clearance.The submerged state has little effect on the horizontal force.When the bottom of the beam is on the static water surface,the peak value of the vertical force is the largest.