Reliability Assessment of Water Networks Considering Spatially Variable Seismic Ground Motion

Water distribution networks are essential lifelines that must remain operational following a seismic event. Pre-earthquake assessment, management, and mitigation of the risk of lifelines is of paramount importance to their owners, i.e. authorities and water distribution agencies in designing, constructing and retrofitting their systems to reduce the damage potential in the light of a future seismic event. The assessment of lifeline capacity is of critical importance for the quick resilience of the city and therefore appropriate methodologies for calculating their reliability are always desirable.

In this work, we discuss a novel approach for assessing the probability of the water not being able to reach every house connection following a seismic event. The proposed methodology gives emphasis on the spatial variability of the seismic ground motion, which past investigations typically assume that is uniform throughout the network. Experience and measurements during past earthquakes has revealed that the seismic demand not only is not uniform, but it may vary significantly depending on the local topography and other parameters. We, therefore, attempt to provide a methodology for a system-wide analysis utilizing component analysis, network topology and methods for assessing the spatial variability of earthquake ground motion. We use graph theory to simulate the damaged network. Graph theory is a versatile mathematical tool that allows to extent the proposed approach to other lifelines (e.g. power, transport) and requires only basic knowledge of hydraulics.