Study On Tsunami Force Of Bridge Superstructure And Anti Tsunami Measures

In recent years,there are many sea-crossing and coastal bridges have been built,started or put on the agenda.The construction and operation of sea-crossing and coastal bridges need to face various severe and complex wave current sea conditions including tsunami and storm surge.The magnitude of the tsunami’s energy,its impact scope and disasters extent are all much larger than storm surges.The Sumatra tsunami in Indonesia in 2004 and Japan’s northeast tsunami in 2011 both left tens of thousands of people dead or missing,and destroyed many bridges,buildings and ports.Relevant studies have shown that some coastal areas of China are facing a certain risk of tsunami.In addition,with the promotion of the "the Belt and Road Initiative",China’s increasing overseas infrastructure projects and infrastructure will also face significant tsunami risks.Bridge is not only the important part of transportation,but also the guarantee of quick rescue after the disaster,which is the key of lifeline engineering.However,there is a lack of relevant provisions about anti tsunami design in bridge engineering specifications.Most of the sea-crossing and coastal bridges that have been built at home and abroad have not been designed for anti tsunami.According to the post-tsunami survey report,the most common types of damage to bridges struck by tsunamis include the superstructure of the bridge is washed away or has a large displacement.Therefore,it is necessary to study the tsunami force on bridge superstructure and put forward reasonable and effective anti-tsunami measures for bridge superstructure.The main research contents of this paper are as follows:(1)Based on ANSYS fluent,a two-dimensional numerical flume is established,and dam break wave is used to simulate tsunami surge.The basic governing equations of numerical calculation and the theory of dam break wave are briefly introduced.Through the comparison with Stoker’s theoretical solution and the data from the PWRI flume test,the flow field characteristics of the numerical simulation dambreak wave and the accuracy of the numerical calculation of the tsunami forces on the superstructure of the bridge are verified.(2)The time history curve of the tsunami force on bridge superstructure is divided in detail,and the time history characteristics and generation mechanism of the tsunami force in each time phase are analyzed in detail.The surface of bridge superstructure is divided,the tsunami forces at different positions of bridge superstructure are monitored,the contribution of the forces at different positions to the overall tsunami force is analyzed,and the mechanism of the tsunami peak force on bridge superstructure is further studied.Furthermore,the effects of different incoming wave heights and different initial clearance heights on the tsunami force on bridge superstructure are studied.(3)The effect of the measure of installing fairing on upstream face of bridge superstructure on the tsunami force on bridge superstructure is studied.The influence of different types of fairings on the peak value of tsunami force on bridge superstructure and the mean value of tsunami force in quasi stationary period are compared.Furthermore,the influence of the fairing with openings on the tsunami force on the bridge superstructure is studied.(4)The effect of the measure of setting air hole on the top plate of bridge superstructure on the tsunami force on bridge superstructure is studied。The influence of different sizes of air holes on the peak value of tsunami force of bridge superstructure and the mean value of tsunami force in quasi stationary period are compared.