Seismic Rehabilitation Optimization of Water Pipe Networks Considering Spatial Variabilities of Demand Criticalities and Seismic Ground Motion Intensities

Abstract

Operation of critical infrastructure facilities such as hospitals, firefighting stations, and disaster shelters are critical during a postearthquake scenario. The serviceability of many such facilities is, in turn, dependent on the proper operation of water-supply systems providing water to these facilities. Due to such dependency of disaster relief systems on water supply, having a resilient water-supply system is even more critical in a postearthquake scenario as compared to a normal operating condition. Extant pertinent literature ignores spatial variabilities of the water demand priorities. It assumes that the water demand originating from critical facilities, such as hospitals and the water demand originating from less critical facilities such as golf courses and temporary storage facilities, are of equal importance. This oversimplification has made existing models practically limited, especially in a postearthquake scenario. The objective of this study is to create a methodology to identify optimized proactive seismic rehabilitation policy for water pipe networks considering spatial variabilities of demand criticalities and seismic ground motion intensities. A novel approach based on proximity analysis was created to determine the criticality of each node where the criticality was established based on the spatial distribution of water demand type in the neighborhood of the node. The spatial variabilities of demand criticalities along with the spatial variabilities of the seismic ground motion intensities integrated into the formulation of a stochastic combinatorial optimization problem to identify economical rehabilitation policies for enhancing seismic resilience of the water-supply network. A purpose-built simulated-annealing algorithm integrated with Monte Carlo simulation was then used to solve the optimization problem. A city-scale water pipe network was used as a testbed to demonstrate the effectiveness of the created methodology. The results of this study and their comparison with results from existing methods showed that the created methodology was highly effective in identifying economical proactive seismic rehabilitation policies for preventive intervention when the rehabilitation budget is limited. Furthermore, the results showed that the consideration of spatial variability in water demand type leads to the identification of rehabilitation policies that ensure higher postearthquake serviceability in nodes supplying water to critical facilities.