Research On Inherent Characteristics And Dynamic Response Of Earthquake Of Submarine Spanning Pipelines

Undersea oil and gas pipelines are the main form of transportation of offshore oil and gas.It plays a vital role in production of offshore oil and gas field. However, due to the complexityof the ocean environment, it’s inevitable for the appearance of submarine spanning pipelines.The spanning would easily result in fatigue failure of pipelines. China’s coastal areas is in theCircum-Pacific seismic belt, and seismic loading has some characters such as short time,high-frequency and big strength which would bring devastating damage to the submarinespanning pipeline. So, the research on the dynamic response of submarine spanning pipelineunder seismic loads has significance for ensuring the safe operation of the undersea oil andgas pipeline.Mainly aimed at the submarine spanning pipeline, works are carried on in three aspectsin this paper.Firstly, mechanical analysis models of single spanning pipelin and double spanningpipeline were established. Inherent characteristics analysis using finite element softwareANSYS was carried out which mainly focus on the influence of span length, environmentalload and boundary soil character. The results showed that the main factors affecting the safeoperation of submarine spanning pipeline are span length and boundary soil character. Theinfluence of environmental load is weak. So, in actual project status, in order to ensure thesafe operation of the submarine pipeline, span length should be controlled and boundaryconstraints should be reinforced. Secondly, research on the dynamic response of submarine spanning pipeline underseismic loads was carried out. The results show that seismic loads in horizontal directionplays a major role on the dynamic response of submarine spanning pipeline.Finally, the formula of critical span length was calculated based on the crosswisevibration equation of Bernoulli-Euler single cross beam. The results show that the boundaryconditions have a big influence on the critical span length. The critical span length ofsubmarine spanning pipeline calculated under fixed constraints is1.5times long than thatcalculated under supported constraints.