Pipelines at Bridge Crossings: Empirical-Based Seismic Vulnerability Index

Past and recent earthquakes have highlighted significant seismic vulnerability of utility lines, including water and wastewater pipelines, at bridge crossings. After the Canterbury Earthquakes (2010-2011), severe impact on utility lines at bridge crossings was reported. To identify the risk mitigation strategies for these systems, a performance based approach for the seismic assessment of integrated bridge-utility systems has been proposed. This paper focuses on findings from the first stream of the proposed framework, by presenting the product of the exhaustive data collection and collation, as seismic vulnerability indices. Firstly, an overview is presented highlighting performance of pipelines mounted on host bridges during the past earthquakes. Subsequently, the methodology employed to evaluate the seismic vulnerability index for pipelines at bridge crossings is presented. The methodology is based on data collation, which employs Geographic Information Systems (GIS) overlays of: the bridge and utility inventory in the Canterbury region; damage observations to bridge and utilities during the Canterbury Earthquakes (2010-11); and, the sustained ground shaking and ground deformation maps. The seismic vulnerability index will provide an initial basis for asset managers for pre-disaster screening and prioritization of existing potable water and waste water pipeline installations on bridge crossings, in seismic prone regions.