Realistic Strain Capacity Models for Pipeline Construction and Maintenance

Main Objective

This work builds up the latest developments in compressive and tensile strain capacity models and extends these models to realistic design and application scenarios. There are two major components (1) development of a unified Strain Base Design (SBD) methodology in which the compressive and tensile strain limit states can be analyzed in a consistent manner, and (2) refinement of existing compressive models to the same level of sophistication and consistency as the tensile strain models. Both new pipeline construction and maintenance of existing pipelines will benefit from the output of this work.

Public Abstract

Pipelines may experience large longitudinal strains in areas of large ground movements. Such movements may come from frost heave and thaw settlements in arctic regions, seismic activities, mine subsidence, etc. For offshore pipelines, large longitudinal strains may be induced by thermal expansion of the pipelines within certain spans. At least two failure modes are possible when pipelines are subjected to large longitudinal strains: tensile rupture and compressive buckling. These two failure modes are treated separately with different levels of refinement in the current industry practice. Some of the newly emerging tensile strain models incorporate the effects of more material and geometric features of pipelines than most compressive strain models used in the industry.
In actual pipelines, the two failure modes, tensile rupture and compressive buckling, interact and work simultaneously. The main objective of this project is to develop a unified approach to the two failure modes and bring the compressive strain design models to the same level of refinement as the tensile strain design models. The industry and regulators are expected to benefit from the outcome of this project through (1) enhanced safety from the refined compressive strain design models and (2) effective allocation of resources to address the varying levels of possible threats to pipeline safety and integrity in the event of large ground movements.