Research On Dynamic Response Of Buried Heating Elbows Under Seismic Waves

With the rapid development of China’s economy, the people’s living conditions hadimproved significantly in recent three decades. As a critical municipal infrastructure, theheating transportation pipeline system (HTPS) plays an important role in metropolis,especially for winter cities in the north of china and high altitude regions. Because ofthe high seismic hazard in recent years in china, the seismic design on HTPS was paidmore attention. Although, Seismic performance of buried pipeline research hasdeveloped more than40years, and had many valuable results and experience, however,limited researches were applied to the HTPS. The researches for the seismicperformance of buried elbow sections which suffer more complex loads than straightpipe were much more tie. To provide more service, heating pipeline system needs to seta large number of steering elbows. So, HTPS was more vulnerable under seismicinvading according to the results from buried pipeline. It is necessary to do someresearch related to the seismic response of heating elbow.The heating elbow seismic analysis modes were established based on the softwareof ANSYS. Adopting the shell-equivalent spring system model, and the equivalentdisplacement method input the seismic shock. The main contents in this dissertationwere included the following:(1) The earthquake damage of buried pipeline was firstly discussed, and thecorresponding researching progress related to buried pipeline earthquake engineeringwas also presented. Then, the development of HTPS in China was reviewed, and thepossible key problems related to the seismic design of HTPS in China were pointed out.(2) A shell-spring model was set up to simulate the seismic response of buriedstraight heating pipeline system and the related model parameters were discussed.Finally, the results based on the steady-state thermal analysis were compared with thetheoretical solution. Model has been proved to be high reliable on simulating theseismic response of the heating pipeline.(3) A DN200heating elbow model was constructed to study its response under theinitial stress and earthquake respectively. The results showed that the initial stresses ofHTPS generated stress concentration on the elbow zone, so did it under seismic load.Straight flexure arms would release the thermal expansion deformation, which washelpful to reduce the maximum stress of the straight pipe under earthquake, but thephenomenon would make the heating elbow more vulnerable in his bending parts.(4) The relationship between the seismic response of buried heating elbow andthese parameter, such as pipeline diameter, radius of curvature of the bending pipe,temperature of heating pipeline, the seismic invading angle, seismic intensity soil spring stiffness, were systematically analyzed. The results proved that the seismic response ofburied heating elbow decreased with the increasing of pipe diameter and decreasedsubstantially with the increasing of radius of curvature of the bending pipe. It meant thata suitably large radius of curvature of the bending pipe is good for decreasing theseismic response of buried heating elbow. The seismic response of buried heating elbowincreased with the increasing of seismic intensity soil spring stiffness. The initial stressof buried heating elbow, stress increment caused by an earthquake, seismic stressamplitude all increased with the expansion of the temperature range. The seismicresponse of buried heating pipeline increased gradually with the increasing of PGA.When the horizontal seismic incident direction was perpendicular to the tube sectionswhich had no fixing devices, the seismic response of buried heating elbow reached themaximum.