Seismic damage probabilities for segmented buried pipelines

Having aging buried pipeline systems, many lifeline utility (e.g., water) companies worried about the performance of their systems against various hazards. For example, water distribution engineers of water utility companies need methodology that would assist in estimating the optimum time to replace water mains. Risk assessment of these systems provides a valuable tool for the mitigation studies. In seismic areas, pipelines are affected by earthquake loading and get some damage. The damage state is controlled by several parameters related to pipeline properties, geological and geotechnical characteristics of the locations where pipelines exist and seismic intensity. Because these parameters show substantial change for a pipeline system, which generally spreads over large areas, geographical information systems (GIS) are used for evaluations. In this study, the fragility relations relating the probability of buried pipeline damage within the pipeline system to the seismic intensity levels were presented. The seismic intensity is represented by peak ground velocity (PGV). The 1994 Northridge Earthquake and Los Angeles water supply system damage database were used to develop the fragility relations. By using the GIS, a grid of different sizes were superimposed on the pipeline damage and PGV maps. Effects of grid size on the damage probability curves were discussed.