| Immersed pipes are often used to transport gasoline,natural gas,tap water and other daily necessities,which are closely related to the life of urban residents.Pipeline construction process is complex and need high technical requirements,once the construction accident will inevitably lead to major risks.During pipeline construction process,submerge pipeline into the base tank is the most core and dangerous stage in the pipeline construction process,when the immersed pipeline construction is restricted by certain equipment and the space,a number of airbags,steel pipe,barges,crawler crane and other auxiliary add to the pipeline.Therefore,pipeline construction faces many problems for multi-bodies coupled.The study based on the fully coupled analysis and nonlinear time-domain dynamic analysis method,Morrison’s hydrodynamic theory,hydrodynamic multi-body coupling theory,long and huge river crossing curved pipeline theory,etc.and the commercial computer program Orca Flex.Systematically study the motion response of the submerged pipe system under the condition of wave and current and the variation of tension of cable and anchor cable.In this study,a multi-floating body coupling straight pipeline model,an marine straight pipeline model and a river-crossing bend pipeline model were established respectively,and the dynamic response of the three models and the law of cable forces during the phase of air bag deflating and immersing into the base tank were calculated.Finally,the time domain images of the dynamic response of the pipeline and the force of the anchor cable and the suspension cable during the process of pipe sinking under various calculation conditions were obtained.The influence of key construction variables and environmental variables on the dynamic response of the three models in the process of pipe immersing was explored,and put forward construction suggestions for different pipeline projects.Results from the numerical analysis can provide valuable safety control technologies and construction recommendations for the project.In this paper,the dynamic response analysis in the immersing process of multi-bodies coupled pipeline is deeply studied,and the following research results are mainly obtained:(1)For long straight pipeline with multi-bodies coupled,the maximum dynamic response appears at the end of air bag deflating,while the maximum Mises stress is appear at both ends of the pipeline.When the pipeline is constructed in still water,the displacement in all directions is small.After further consideration of the flow velocity,the Mises stress at the middle of the pipeline decreases.The velocity has different effects on the displacement in each direction,but the effect on the cable force is negligible.Therefore,the construction scheme can be adopted to reduce part of the barges,increase the constraints at both ends.(2)In the Marine environment The dynamic response of the long straight pipeline with multi-bodies coupled was studied.The results show that the velocity is not directly proportional to the cable force and Mises stress,but is directly proportional to the sway.The wave height is proportional to cable force,pipeline sway and pipeline Mises stress.When the incident Angle of the wave is large,it is unfavorable to the construction safety.The wave period has little influence on the cable force,but great influence on the pipeline sway and Mises stress.When the wave is irregular,the effect is greater at the initial stage of the outgassing.(3)Different from the straight pipeline model,long bending pipeline with multi-bodies coupled will appear the tension-relaxation phenomenon at the cable in the process of immersion.As a result,part of the cable is too heavy,and the other part is too slack,which may lead to engineering accidents.The maximum pipeline bending moment and Mises stress appear at where pipeline bending angle largest.In view of this,the pipeline should be deflated and lowered at same time,set a small pretension,and moderately extend the deflated time. |
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