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Chapter 13

Reliability-Based Strength Design of Pipelines

13.1 General

A technical revolution in the design process is taking place in the pipeline industry as a result
of new codes, e.g. IS0 DIS 13623 Code (IS0 1997), and other codes. Advanced methods and
analysis tools allow a more sophisticated approach to design that takes advantage of modem
materials and the revised design codes. A “Design Through Analysis” (DTA) approach has
been developed by Bai and Damsleth (1998) where the finite element method (FEM) is used
to analyze global behavior as well as local structural strength of pipelines. The structural
reliability method is used to determine the partial safety factors used in the finite element
analyses.

Reliability-based limit-state design principles are described in NORSOK Standard Y-002 and
will be issued as an IS0 guideline. Advanced engineering based on EM and structural
reliability are increasingly demanded by design projects to meet new challenges such as
deepwater, High PressureMgh Tempcrature (WEIT), new materials, harsh environments
and reassessment of existing pipelines.

A pipeline design typically involves the following technical aspects:

route optimization
wall-thickness design
on-bottom stability analysis
installation analysis
upheaval and lateral buckling design
free-spans design for vortex-induced vibrations (W) and fishing gear impacts
seabed intervention design
constructions such as tie-in and pipeline crossings

Bai and Damsleth (1998) demonstrated that reliability-based limit-state design may be applied
to the above technical aspects of pipeline design.