Study On The2.5D Fluid-structure Interaction And Its Engineering Applications Of Large-scale Aqueduct

This paper presents the2.5D fluid-structure interaction (FSI) model of aqueduct, due tothe limitations and problems of existing models. A simply supported U-shaped aqueduct isintroduced in the numerical analyses to study the2.5D FSI model and compare it with typical3D FSI models in the dynamic and static analysis of aqueduct. The results show that thismodel has good simulation results for dynamic and static analysis of aqueduct-water couplingsystem. And the torsion effect of a multi-span aqueduct body under the lateral seismicexcitation is studied by the numerical analysis of fluid-structure interaction. Finally, athree-span aqueduct with unequal height piers is introduced to study its structural responseunder the horizontal, orthogonal and bidirectional seismic action. The main work andconclusions in this paper are shown as follows:（1）The2.5D fluid-structure interaction model of aqueduct is established. This model isbased on the existing modeling methods of aqueduct, structural dynamic analysis theory andfluid-structure interaction theory, combing plane problem with space problem. Comparedwith existing models, the2.5D FSI model of aqueduct can effectively reduce the orders ofnon-linear fluid-structure interaction equations to improve its computational efficiency, whichis practical in the large-scale calculation of multi-span aqueduct.（2）The static structural response of large-scale aqueduct is analyzed with2.5D FSImodel. A simply supported U-shaped aqueduct is introduced in the static structural analysis.The numerical results show that under static loading, the2.5D FSI model presented in thispaper not only can well simulate the displacement and internal force of aqueduct body, butalso can well simulate the water pressure acting on the aqueduct interface wall and reflect the3D coupling effect. Therefore, the2.5D FSI model can meet the requirement of precision inthe static analysis of aqueduct, and can obtain good simulation results with appropriateselection of the amount of coupling planes.（3）The dynamic structural response of large-scale aqueduct is analyzed with2.5D FSImodel. A simply supported U-shaped aqueduct is introduced in the dynamic structuralanalysis based on the above static analysis. The numerical results show that under dynamicloading, the2.5D FSI model presented in this paper not only can well simulate thedisplacement and internal force variation of aqueduct body, but also can well simulate thewater pressure variation acting on the aqueduct interface wall and reflect the3D couplingeffect. Therefore, the2.5D FSI model can meet the requirement of precision in the dynamic analysis of aqueduct, and it is time saving and practical in engineering applications.（4）The torsion effect of large-scale aqueduct is studied. The study is focused onwhether the difference in the stiffness of piers and the support conditions of each span ofaqueduct causes bad torsion effect of aqueduct body. Though there is difference between theend supports’ stiffness of each span of aqueduct, the torques have little difference, whichmeans that the difference of supports’ stiffness has little influence on the torque internal forceof aqueduct body. In the design of a simply supported aqueduct, the mid-span section internalforce is usually adopted as the design threshold of the aqueduct body. During the earthquake,the mid-span section internal force is the maximum of internal force. Therefore therequirements of seismic safety for entire aqueduct body can be met if the mid-span sectioninternal force is adopted as the design threshold.（5）The horizontal and bidirectional seismic response of large-scale aqueduct is studied.A three-span aqueduct with unequal height piers is introduced to study its structural responseunder the horizontal, orthogonal and bidirectional earthquake action in the general finiteelement program ADINA, adopting the dynamic time-history method and fluid-structureinteraction numerical method. The results show that the vertical displacements, verticaldeformation and vertical moments of aqueduct body under the bidirectional seismic action arevery similar to those under the lateral seismic action alone, and are little influenced by thelongitudinal seismic action. Compared with longitudinal or lateral seismic action alone, underthe horizontal and bidirectional seismic action, the increase of the maximum values of sectionprincipal stress is obvious. Therefore, horizontal, orthogonal and bidirectional seismic actionshould be considered in the design of aqueduct.