Research On Seismic Response Mechanism Of Oil-gas Medium-pipelinecable-stayed Pipe Bridge Coupling System

The lateral stiffness of the cable-stayed pipeline bridge structure supporting oil and gas pipelines is much smaller than that of the traffic crossing structure,and the structural damage is more serious in earthquake disasters,in order to improve the seismic design specifications of pipeline engineering and ensure the safe operation of spanning oil and gas pipelines,on the basis of investigating the structural characteristics of a large number of cable-stayed tubular bridges,this paper takes an oil pipeline supported on a cable-stayed spanning structure as an research object,the finite element model structure of the full-scale cable-stayed pipeline bridge structure system was established,the seismic response of the cable-stayed pipeline bridge structure considering two kinds of fluid-solid coupling effects of the steady state of the medium and the time-dependent mechanical behavior of the medium is explored,revealed the seismic response mechanism of the cable-stayed spanning oil and gas pipeline considering the fluid-solid coupling effect,it provides a theoretical reference for the experimental research and field test of the cable-stayed pipeline bridge structure.The main research contents and conclusions are as follows:(1)Based on the dynamic theory of cable-stayed spanning oil and gas pipelines,with the background of actual engineering,through finite element calculation software,the additional mass method,the typical model of fluid-solid coupling dynamics,and the finite element model of the cable-stayed pipeline bridge structure considering the time-dependent mechanical behavior of the oil-gas medium were respectively established,and analyze the dynamic characteristics.(2)Based on the theoretical basis of time history analysis,in the seismic response of the cable-stayed pipeline bridge structure considering the steady-state fluid-solid coupling effect,the calculation results of 4 points of the pipeline model located at the mid-span section of the bridge platform and part of the support are extracted,the displacement,acceleration time-history curves and peak values of the additional mass method and the steady-state fluid-solid coupling dynamic model are obtained.the results show,the seismic response results of the pipeline using the added mass method are stronger than those of the FSI method;The seismic response of the pipeline section reaches the maximum at the position near 1/5 of the left bridge platform;In the seismic response of bridge platform mid-spanning pipe section,among the 4 points in the section,the seismic response of point B reaches the maximum;In the seismic response of partially supported mid-spanning pipe section,among the 4 points in the section,the seismic response of point D reaches the maximum.In oil and natural gas transportation projects,vertical fracture of pipelines should be prevented.(3)Seismic response time-history analysis of cable-stayed pipeline bridge structural system considering time-dependent mechanical behavior.A kinetic equation considering the timedependent mechanical behavior of the medium is proposed,and change the turbulence model and the dynamic mesh update model of the fluid domain,analyzed and extracted the displacement,acceleration response and peak value of the point D of the pipeline section at the mid-span position of the bridge platform and some supports.The results show,the displacement response reaches the maximum at the position nearly half of the right bridge platform,the acceleration response reaches the maximum at the right half of the oil and gas pipeline model close to the main tower.(4)The seismic response of the oil and gas pipeline considering the oil-gas medium timedependent mechanical behavior is compared with the seismic response of the steady-state fluidsolid coupling effect.The results show,the seismic displacement responses of both are small at the bridge platform position,considering the displacement response of the steady-state fluidsolid coupling effect,is twice that of the fluid-solid coupling effect considering the timedependent mechanical behavior of the medium,but its acceleration response is smaller than the unsteady fluid-solid coupling effect,the flow of the medium in the pipe has a complex effect on the seismic response of the oil and gas pipeline.