Seismic Concerns for the Design of Above Ground Pipe Supports

Abstract

Current pipeline design practice within water pipeline industry is largely based on the American Water Works Association (AWWA) design manuals, which do not address seismic design explicitly. Pipeline designers often use seismic design guidelines published from other sources, such as American Lifelines Alliance (ALA) and American Society of Civil Engineers (ASCE) and building codes such as International Building Code (IBC). The guidance presented in the current ALA and ASCE seismic design guidelines are outdated, as the building codes and seismic hazard maps have been updated few times since the publication of these documents. Although outdated, the concepts and guidance presented in the ALA and ASCE seismic design guidelines, specifically with regard to the establishment of seismic design criteria for a pipeline based on its function and use, are still applicable. The seismic design criteria of a pipeline should be established by considering the performance objectives, such as serviceability, damage control, and collapse prevention. The goal is to ensure life safety performance, while providing an economically feasible design with an acceptable level of functional reliability following a seismic event. To achieve reliable performance of an above ground pipeline segment, the seismic stability of the ground as well as the structural performance of the support should be evaluated by the designer for the intended seismic performance level and criteria. The interdependence of the soil-structure interaction performance during a seismic event should be evaluated and accounted for, with input from both geotechnical and structural engineers. This paper presents a brief summary of the currently used and published seismic criteria in other design practices, presents an approach to determine appropriate seismic hazards for the design of the pipeline and for the evaluation of the ground hazards, and a discussion of seismic design concerns associated with the design of an above ground support.