NEHRP Clearinghouse

Title
Effect of Local Inhomogeneity on the Dynamic Response of Pipelines.
File
PB81122533.pdf
Author(s)
Nelson, I.; Weidlinger, P.; Baron, M. L.
Source
National Science Foundation, Washington, DC. Engineering and Applied Science., October 1979, 106 p.
Abstract
The dynamic axial response of long segmented pipelines induced by incoherent seismic ground motion in inhomogeneous soil conditions is reported. Seismic response of pipeline 'lifelines' is important because of the potential grave consequences of an earthquake disruption of vital services. Results indicate that, in general, a local inhomogeneity may contribute to a change in pipe response in three different ways: (1) a local variation in delay time in the case of wave propagation; (2) a variation in the free field waveform at adjacent segments caused by inhomogeneity; and (3) a variation in soil stiffness from soft to firm material. All three effects generally occur simultaneously. Changes in the phase delay are not significant. Large amplifications in pipe response, relative to the homogeneous case, can occur when the incoherent component of the input ground motion is large. For a two degree of freedom system, a local change in soil stiffness can cause a large increase in pipe response, even for a coherent ground input. A two degree of freedom system appears to be a reasonable model for the behavior of a multisegment system.
Keywords
Dynamic response; Ground motion; Earthquake engineering; Pipelines; Earthquakes; Soil dynamics; Earth movements; Seismic waves