Seismic Analysis of Buried Steel Pipeline Subjected to Ground Deformation with Emphasis on the Numerical Modelling Optimization
Proceedings Publication Date
Steel pipeline systems traverse large geographical areas characterized by a wide variety of soil conditions and environmental hazards such as earthquakes which can threaten the pipeline integrity undergoing large deformations associated with widespread yielding, leading to fracture with consequent material leakage. Buried pipelines installed in seismic regions are susceptible to the effects of transient ground deformation (TGD) due to seismic wave propagation and permanent ground deformation (PGD) resulting from earthquake induced soil liquefaction, surface faulting and landslides . Post-earthquake investigations have shown that almost all seismic damages to buried pipelines were due to permanent ground deformation and there were very few reported cases of pipelines damaged only by wave propagation . In fact, buried pipelines are primarily affected by large permanent ground deformations (PGD) which may produce pipe wall rupture due to excessive tension as well as buckling by either excessive imposed bending or uniaxial compression loading. Therefore it is necessary to perform accurate finite element analysis taking into account the nonlinear soil and pipe interaction as well as the constitutive behavior of the pipe material subjected to extreme seismic loading. At the state of art, detailed finite element analysis of the soil-pipeline system subjected to large ground deformations are computationally expensive resulting in extremely large numerical models that may require days to run using the normally available computational resources . Within the present work, in order to reduce the needed memory and computation time of the calculator, the part of the soil-pipe system away from the fault is suitably modeled as a single equivalent axial spring, connected to the pipe shell elements through appropriate constraints. Furthermore, the seismic performance of the buried pipeline has been investigated through a series of parametric studies that permit to assess the structural response of the pipe components in function of various configurations of the soil-pipeline system. The obtained numerical analysis results allow to evaluate accurately the limit ground displacement inducing global failure on the pipeline components due to loss of strength capacity following large scale seismic loading, with the advantage of being computationally efficient.