Axial Connection Force Capacity Required for Buried Pipelines Subjected to Seismic Permanent Ground Displacement

Buried pipelines are susceptible to damage from ground movements triggered by earthquakes, such as liquefaction-induced lateral spreading, landslides, and fault rupture. Given the linear characteristics of water and wastewater pipelines, failure due to ground displacement is most likely to occur at locations of weakness, which for segmented pipelines is typical at joints or fittings linking adjacent sections of pipe. Connections can be characterized as unrestrained (e.g., bell-and-spigot joints), fully restrained (e.g., continuous systems with welded/fused connections), or hybrid segmented joints, which provide the ability to displace axially in response to ground movement before locking up and behaving as a continuous system. The joint type and geometry will contribute significantly to the expected performance of a given pipe system subjected to axial and/or transverse ground movements. Furthermore, the connection force capacity of the joints is an important limit state for predicting failure of pipe systems for which the joint has less strength than the pipe barrel. To support the development of an ASCE/UESI manual of practice (MOP) on Seismic Design of Water and Wastewater Pipelines, this paper presents a framework for establishing the minimum connection force capacity (based on burial conditions and pipe/connection characteristics) required for a particular system to be classified in one of four proposed seismic demand categories defined by the MOP. To predict system response to various levels of ground movement, an analytical model is paired with a statistical approach to compare the survival rate of pipe systems that have performed well in past earthquakes to the expected survival of other systems composed of different materials and mechanical connections. Results will aid seismic capacity classification by providing a basis for establishing connection force capacity coefficients for new and existing systems.