Seismic Wave Effects on the Longitudinal Forces and Pullout of Underground Lifelines

This paper describes a general model for the longitudinal force and pullout induced in underground lifelines in the form of pipelines/conduits by seismic waves. The model accounts for the effects of both body and surface waves, and provides a definition for conduits that are either relatively rigid or flexible in the axial dimension with respect to seismic ground deformation. Both finite element and simplified models are presented that account for the effects of peak ground velocity, wave propagation velocity, predominant period of seismic excitation, shear transfer between soil and conduit, axial stiffness of the conduit, and pullout and compressive capacity of conduit joints. Modeling results for water trunk line performance during the 1994 Northridge earthquake are shown to compare favorably with observed pipeline behavior during that earthquake. In total, 320 finite element runs were performed to account for different combinations of ground conditions, pipeline properties, and seismic wave characteristics. Dimensionless plots were developed from the simulations that facilitate the computation of relative slip at pipeline joints and connections between tunnels and underground facilities. Copyright © (2006) by Earthquake Engineering Research Institute All rights reserved.