Numerical Simulation of the Behavior of Buried Jointed Pipelines under Extremely Large Fault Displacements

A comprehensive numerical method for limit state simulation of buried jointed pipelines is presented. The pipe body is modelled by line elements and plastic deformation within it considered by plastic hinges. The basic mechanical properties of all common pipe joints e.g. stiffening in compression, detachment in tension, fracture in bending can also be considered. Soil-pipe interaction is modelled by elasto-plastic direct and drag springs. The method is capable of tracing the behaviour of pipelines until and after failure of the pipe body and detachment at joints, thus allowing the physical damage to a pipe network to be better estimated. The method is three-dimensional, thus allowing the interaction of pipeline segments running in different directions to be evaluated as well. The solution algorithm is based on the direct integration of uncoupled equations of motion, which ensures that the behaviour of a pipeline can be investigated for any magnitude of ground displacements, revealing the whole spectrum of events occurring in the pipe-soil system with the increase of earthquake induced ground displacements: elastic deformations, plastic deformations in the soil, plastic deformations in the pipe body, rupture and detachment at joints, failure and rupture within the pipe body. The method is implemented into a computer program and several trial runs are presented.