Failure criterion for buried pipe subject to longitudinal PGD : Benchmark case history

ABSTRACT

The effects of longitudinal Permanent Ground Deformation (PGD) on a buried continuous steel pipeline is considered. Longitudinal PGD, (ground movement parallel to the pipe's axis) is characterized by the amount of movement, & and its spatial extent, L. Local compressional buckling of the pipe wall and tensile failure of pipeline are taken as the failure modes of interest. Critical values for the amount of ground movement and the spatial extent, which lead to compressive failure, &cr and Lcr, are determined for five grades od steel, various R/t ratios and burial conditions. Three buried pipelines which were subject to longitudinal PGD during the 1994 Northridge California event are used to benchmark the proposed failure criterion. The proposed analytical procedure suggest that two of the three pipes, the Los Angeles Dept of Water and Power Granada Trunk Line and the So. Cal. Gas (SCG) Line 120; both located along Balboa Blvd. at the Northern and of the San Fernando Valley would suffer damage. The observed behavior matches the predicted behavior. The third line, the newer SCG line along McLennan Ave., is also considered. For the third line, we postulate as to why it was not damaged. There are two other lines along Balboa which were undamaged by the PGD. These two lines are excluded from consideration because of a lack of information on certain parameters. Finally the effects of an expansion joint which was installed in the LADWP line after the 1971 San Fernando earthquake are discussed in detail.(AU)