Fluid-structure Interaction Dynamic Analysis Of Pier Under Shoaling And Breaking Waves

Wave is one of the main loads of sea-crossing bridge,which is different from land bridge.It is also an important load considered in the design stage of sea-crossing bridge.In shallow water areas,when the wave propagates from the open sea to the nearshore places where the sea-crossing bridge is located,the wavelength becomes shorter and the wave steepness increases with the sharp shallowing of the water depth.When the horizontal velocity of the water particle of the wave crest exceeds the wave propagation celerity,the wave will curl and break in a very short time,releasing huge energy and imposing huge load on the marine structure.The breaking wave only lasts for a short time,so its energy is mainly concentrated in the higher frequency.When it impinges the pier of sea-crossing bridge,it is likely to cause high-frequency resonance and amplify the dynamic response of the structure.In this thesis,the ultimate wave steepness of wave breaking is studied experimentally and numerically.The reaction and response of breaking wave impacting pier under coupling condition are analyzed.The main research contents include:(1)A slope terrain was built in the wave-current flume of Southwest Jiaotong University,the relationship between wave steepness limit and wave parameters is studied while shoaling.Set the relative breaking water depth and breaker indexγ_b as the research object,the flume test data is compared with the previous formula.(2)Based on the computational fluid dynamics software Fluent,a numerical flume is established,and the accuracy of the flume is evaluated by using the uncertainty analysis method.The independence of grid and time step is verified.The flume can also be used for subsequent FSI research.Taking the incident wave height,period,water depth and slope gradient as parameters,the fitting formula of breaker depth index which is suitable of flume test conducted in the thesis is developed.(3)Based on Workbench,the Fluid-structure interaction analysis of breaking wave impacting pier is carried out.Referred to a sea-crossing bridge,the coupling between breaking waves and piers under strong and weak coupling conditions is compared,and the effects of section shape and natural frequency on response are studied.The analysis shows that the strong and weak coupling conditions have little influence on the cases involved in this thesis,the force reaction of the pier structure under the coupling condition is less than that under the uncoupled condition,and the pier force reaction is sensitive to the pier section shape.(4)The finite element model is built for researching the force reaction and response of piers with different sections and different natural frequencies under the breaking waves,which is loaded with the pressure history calculated in Fluent.The analysis shows that the response of piers with different frequencies is different;When the structure frequency is close to the wave frequency,the dynamic amplification effect can not be ignored.