Slippage-Based Seismic Design Approach for Critical Ductile Iron Pipe Hospital Supply

Providing water supply to critical customers such as hospitals following major natural disasters like earthquakes is of the utmost importance. When the hospitals are located near a fault source, the ground motion parameters that must be accommodated can be extreme. This work serves as a proof-of-concept effort to illustrate how a ductile iron pipe near a fault source can be designed to be operational following such an event. The hospital considered in this work is a major regional hospital located within the Tualatin Valley Water District (TVWD) service area, which is located on the west side of the Portland, Oregon, metro area. The approach described for the seismic design procedure is based on pipe slippage loads combined with operational pressures that use procedures developed as part of the $1.6 billion Willamette Water Supply Program (WWSP). While the WWSP procedures for seismic design developed for ductile iron pipe are based on the magnitude 9.0 Cascadia Subduction Zone earthquake, the procedures described by this work are for more severe ground motions due to the hospital's proximity to the crustal Portland Hills Fault, which if it ruptures could be similar to the earthquake that occurred in Kobe, Japan, in 1995. This approach uses a pipe slippage-based seismic design procedure accounting for extreme transient ground shaking, high internal pressures, and operational forces and illustrates how they are specifically accounted for with the fittings and appurtenances that are required with the critical supply pipe to the hospital. Finally, results are compared to the ISO Standard 16134-related seismic performance requirements for ductile iron pipe.