Fluid-Structure Dynamic Coupling's Analysis Of Large Scale Aqueduct

The fluid-structure dynamic coupling of large-scale aqueduct is a very complicated problem which is relative to a good many disciplines. Because it involves two mediums—fluid and solid which have completely different characteristic, it is very difficult to study and there are still many shortcomings in the fields of theory, computing method and application. However, it is always met in engineering. Therefore, it is necessary for us to study the problem deeply.Considering the influence of fluid's viscosity and large amplitude slosh (nonlinear slosh), the 3-dimension coupling system composed of uncompressible viscous fluid and ideal elastic structure is studied in this paper. The moving state of the interface between the fluid and the structure is analyzed, and the boundary's moving condition (i.e. displacement compatibility) and dynamic condition (i.e. traction equilibrium) are given. The fluid-structure coupling system is divided into elements, finite element method equations are deduced and corresponding time integration methods are given. The fluid-structure dynamic coupling analysis method is proved correct by the water tank's example.The flow direction's fluid-structure dynamic coupling problem of large-scale aqueduct under the effect of earthquake which is concerned but not well validated in engineering is discussed using the forenamed fluid-structure dynamic coupling model. The results show that when considering fluid's influence in the flow direction the seismic response of aqueduct structure decreases slightly. Therefore, it is safe without considering the influence in actual engineering. In addition, the applicability and accuracy of additional mass model and Housner model which are widely used in actual engineering are studied. The seismic response results show that most parts'results of structure computed using these two models are conservative comparing with the fluid-structure dynamic coupling analysis method. By contrasting aqueduct structure's self-vibration frequencies and mode shapes between the additional mass model and the fluid-structure dynamic coupling analysis method, it can be found that these two method'sresults are very close, so adopting the additional mass model to analyze aqueduct structure's dynamic property can meet engineering's requirement.As engineering application, this paper discusses the static and dynamic response of the thin shell aqueduct in the middle line of South-to-North Water Diversion Project using the fluid-structure dynamic coupling analysis method which is given in this paper and the additional mass model which is adopted in the project. By contrasting the two method's results it can be found that there are nearly same trends in the changes of aqueduct's displacement and stress and the additional mass model's values are larger slightly than the fluid-structure coupling analysis method's, but the difference is not significant which can be neglected in actual application. Therefore, it is reasonable and feasible to adopt the additional mass model in large-scale aqueduct's seismic design. And the results also show the fluid-structure coupling analysis method's correctness.