| The prestressed concrete cylinder pipes(PCCP)are widely used in various engineering fields because of their advantages,such as the urban lifeline engineering and the large water resources project — the South-to-North Water Transfer Project,which are closely related to the people’s life.But most researches still stay on the static analysis.As the natural disasters such as earthquakes occur frequently,the analysis of earthquake response of PCCP is particularly important considering the earthquake action,and the space and time effect.Based on the project of Henan province “PCCP key technology research”,basic thoughts of the finite element method were adopted and the calculation model of PCCP in Nanyang section of the South-to-North Water Transfer Project was established.The dynamic response of the PCCP under seismic action was obtained through the time history analysis.The following influences were considered in the analysis: the non-uniform field and uniform field,the different seismic wave characteristics(incident angle,peak displacement and acceleration peak value),and the pipe properties(different buried depth and different wall thickness and concrete strength).Finally the various factors of the influence on the dynamic response of the PCCP under seismic action were analyzed and compared.Now the main research conclusions of the paper are summarized as follows.(1)Influences of three different artificial boundary conditions(simple boundary,viscous boundary and equivalent visco-elastic boundary)on seismic response of the structure were compared with the actual seismic damage,and the results show that the equivalent visco-elastic boundary or equivalent uniform visco-elastic boundary is the most suitable artificial boundary reflecting the actual situations.(2)The influence of different field on structure dynamic response is that,the seismic response of the underground pipeline section in the non-uniform field is greater than that in the uniform field,and the more uneven the ground,the greater the dynamic stress of seismic response of the pipe line.Under the uniform field,the stress and displacement values of PCCP are gradually increased with the change of soil conditions from hard to soft(from silt sand to silt and to clay),.(3)The influence of the characteristics of seismic wave(incident angle,peak displacement and acceleration peak value)on PCCP are: dynamic stress of pipeline decreases with the increase of incident angle,the dynamic stress is the largest when incident angle equals zero,.The dynamic stress of the pipe depends mainly on the displacement value of the seismic wave.The maximum axial stress and the maximum bending stress increase with the increase of the seismic wave peak displacement,and the linear change law can be observed.Besides,the axial stress variation is larger than the bending stress variation.The change of seismic wave peak acceleration has hardly influence on structure dynamic stress.(4)The influences of the buried depth and the thickness of pipes on structure dynamic response are that: as the change of buried depth,the structure dynamic stress is almost the same,i.e.,the dynamic stress of the structure has hardly relation with pipeline buried depth;However,when the wall thickness changes,the maximum axial stress of pipe will decrease with the increase of pipe wall thickness,and the maximum bending stress increases slightly but changes little.Changing the stiffness of pipe(wall thickness and concrete strength),displacements of earthquake response are basically the same.So in the future engineering construction,enhancing the pipe stiffness(increase the strength of the concrete pipe core)can not improve the seismic performance of the system.Reducing wall thickness of pipeline appropriately could improve the seismic performance.The results obtained in this paper are in conformity with earthquake damage investigation conclusion,and the research results and conclusions can be used for reference in the later underground building aseismic design. |
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