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Numerical Analysis of Buried Pipelines Strengthened by FRP Subjected to Reverse Faulting

Kazemi, Farshad | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44638 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Rahimzadeh Rofooei, Fayaz
  7. Abstract:
  8. Buried pipes are among the most important urban infra-structures which are developed to distribute water, gas, oil, etc.. Researchers have already demonstrated that extreme failures which lead to total disruption of the pipelines, both mains and the distribution network, due to permanent ground displacement in fault zones. In order to avoid any disturbance in the regular performance of pipelines and prevention of environmental contamination, there is a need to investigate the vulnerability of pipelines and their seismic retrofitting, if necessary. In the presented study, the method of pipeline retrofitting by high strength CFRP composite is investigated. In that regard, using a 3D model of soil-pipe-composite system, different factors effecting the pipe behavior is studied. The pipe diameter, pipe diameter to thickness ratio, soil internal friction angle, fault angle in vertical direction, fault angle in horizontal direction, composite thickness to allowable displacement capacity of the pipe according to ALA regulations, ovalization factor and beam buckling locations from fault area were among the parameters considered for the sensitivity analyses. Soil is modeled using 3D Solid elements, while Shell elements were considered for modeling the CFRP and pipes, neglecting the effect of pipe and CFRP separation. For parametric studies, the numerical models were analyzed using finite element software ABAQUS 6.10.1. Investigations for models with different vertical fault angles of 50, 60, and 70 degrees, pipe diameter to thickness ratios of 36, 26 and 54, and composite thicknesses of 6, 4, 2 and 8 millimeters were carried out. Results indicate that pipe retrofitting changes the local buckling behavior of the pipe to beam buckling. As the results indicate, the compressive strain in compressed part of pipes main factor controls the behavior of buried pipes in reverse faults, and the most effective parameter in this case is the pipe thickness (diameter to thickness ratio). It is also observed that thin steel pipes buckle in smaller fault offsets in compare to the thicker ones. Also, the seismic behavior of the pipes improves and the induced strains decreases as the composite thickness and vertical fault angle increases
  9. Keywords:
  10. Buried Pipline ; Permanent Ground Deformation (PGD) ; Soil-Pipe-Composie System ; Reverse Faulting ; Carbon Fiber Reinforced Polymer (CFRP)

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