Three-dimensional Seismic Pounding Response Analysis Of Large-scale Aqueduct Structures

Pounding phenomenon between two adjacent aqueduct girders is easy to pose a fearful threat to its water conveyance safety under strong earthquakes. To effectively carry out the seismic pounding response analysis research on large-scale aqueduct structures is of great practical significance. By virtue of pounding element model, which is a bridge to pounding numerical simulation, the seismic pounding response of aqueduct structures is reproduced and some possible factors that may affect the impaction as well as their corresponding influential effects are explored in this dissertation in order to provide reference to seismic design of large-scale aqueduct structures and to lay a foundation for its further pounding control studies.On the basis of a review on research actuality of beam structures’pounding issues at home and abroad combined with commonly used methods of seismic pounding response analysis, this dissertation mainly accomplishes three aspects of work as follows:1) A pounding element model of an aqueduct structure through development of FORTRAN programs based on3D Contact-friction theory is established. And then the general3D seismic pounding response analysis program considering boundary penetration that is adapted to thin-walled characteristics of aqueduct structures is developed after assembling the pounding element into finite element program which is developed for seismic response analysis of large-scale aqueduct structures using thin-walled beam segment element and elastic beam-column element.2) A certain aqueduct structure in the middle route of South to North Water Transfer Project is taken as an example and its overall dynamic analysis model is built. Then its pounding response analysis under earthquake excitations is carried out to explore the law of impact on aqueduct earthquake response and seismic performance due to pounding effects via the developed procedures for seismic pounding response analysis of aqueduct structures.3) A comprehensive study of factors that may affect the aqueduct seismic pounding response and their respective impact effect is conducted by changing certain parameter values, such as the angle of seismic wave input, the width of expansion joints, earthquake peak accelerations, site conditions, static and dynamic friction coefficients and water depth in aqueduct, etc. Moreover, the law of impact on pounding response on account of different attachment methods of water to aqueduct body is studied through carrying out the3D pounding response analysis of aqueduct structures considering the fluid-solid coupling effect.The results of the research are as follows:1) Pounding phenomena are extremely harmful to aqueduct structures’ seismic resistance and the huge impact forces will notably complicate their earthquake responses. Besides, poundings may change the pier columns’ ductility demands as well as the bearings’ relative displacement amplitudes and lead to an obvious increase of beam end acceleration responses but a trend to diminish the velocity and displacement reactions.2) The longitudinal seismic input is the control load of aqueduct structure’s pounding responses. The increase of expansion joints’width can greatly reduce the occurrence possibility of poundings but will significantly increase the peak pounding forces. The aqueduct pounding response takes on distinct spectrum sensitivity to seismic waves. Friction has little effect on longitudinal seismic response but much influence on transverse displacement response and adjacent girders’ relative rotation angle. When water depth in the aqueduct increases, the pounding times and pounding forces coupled with relative rotations of adjacent girders and its whole seismic responses will be universally increased.3) Whether making the water in the aqueduct consolidated or considering the fluid-structure interaction makes little difference to peak pounding responses, but the time history curves are quite different. Furthermore, some parts of the structure’s analysis results with water consolidated may be smaller than with considering the fluid-solid coupling effect, and thus may result in the simplified consolidation results tending to be somewhat unsafe.