Seismic Response Modeling of Water Supply Systems

Keywords: Water supply systems. Los Angeles Department of Water and Power (LADWP). Damage. Lifelines. Models. Hydraulic network analyses. Seismic isolation systems.

Abstract: This report presents a comprehensive model for simulating the earthquake performance of water supply systems. The model is developed in conjunction with the water system operated by the Los Angeles Department of Water and Power (LADWP) and validated through comparisons to observations and flow measurements for the heavily damaged LADWP water supply after the 1994 Northridge earthquake. The earthquake performance of damaged water supply systems is simulated using hydraulic network analysis that uses an iterative approach to isolate the network nodes with negative pressures. The isolation process accounts accurately for reliable flows and pressures in the negative pressures. The isolation process accounts accurately for reliable flows and pressures in the damaged water networks by removing unreliable flows and identifying those portions of the system requiring mitigation. An analytical model is developed to predict the effect of seismic waves on underground pipelines. The seismic performance of the LADWP system is simulated using a multi-scale technique in which the LADWP trunk system is explicitly accounted for, while the remaining distribution lines are simulated through fragility curves relating demand to repair rate. The repair rate, in turn, is correlated with peak ground velocities, and fragility curves are developed on the basis of distribution network simulations. The proposed model in integrated into computer code, Graphical Iterative Response Analysis for Flow Following Earthquakes (GIRAFFE) developed by the authors, which presents the simulation results in GIS format.