Using API Line for Improved Seismic Performance of Water Transmission Mains

Pipeline design criteria and performance objectives have advanced with the better understanding of expected damage and consequences. Municipal agencies are being tasked with building systems to meet operational concerns following the maximum considered earthquake. Accepting deformations and exceeding yield stress is common in building seismic design. With properly specified materials, pipeline seismic design can benefit from a similar approach. There are few standards available for engineers to use when designing water pipelines for large deformation due to earthquakes. Typical water industry design practice considers a stress-based design approach, where the pipeline is sized to meet an allowable elastic stress limit. Finite element modelling can utilize steel’s non-linear properties for seismic design. Generally, the optimum behavior for analyses to seismic load conditions is a “round-house” shape stress-strain curve above yield. Using API line pipe, designers can improve designs to accommodate large ground deformation with more predictable performance. ASCE is currently developing a Manual of Practice for Seismic Design of Water and Wastewater Pipelines. These standards encourage engineers adapt available tools when modelling complex soil structure interactions and developing cost efficient, reliable pipeline seismic designs. This paper presents history of pipeline seismic design including a look ahead at the new UESI Manual of Practice, available design methodologies for large PGD, and Portland Water Bureau’s specification to accommodate large ground deformation at the Willamette River Crossing design build project.