Global Buckling Design of Submarine Pipelines: Design Performed Based on DNV-RP-F110

Abstract

DNV-RP-F110 was issued in October 2007 and gives design criteria for expansion caused by internal pressure and temperature. Three different scenarios are considered in the RP; the first and second scenario give criteria for situations where the expansion forces are released by global buckling on even and uneven seabed, respectively, while the third scenario is when the expansion forces are restrained. This is the first public document ever to provide design criteria for situations where the expansion forces are released by global buckling. The first revision of the JIP project specific guideline that constitutes the basis of the RP was issued in 2001 and it is hence “Field proven”. This paper will illustrate different design impacts based on the RP for the even and uneven seabed scenarios. Global buckling design is associated with large uncertainties in important design parameters which include pipe-soil resistance, stress-strain curve and possible interference loads (trawling). These uncertainties are treated systematically in DNV-RP-F110, and the approach leads to a consistent safety level in line with the general requirements in DNV-OS-F101. This paper elaborates how the design may be performed by adopting the principles in DNV-RP-F110. Key aspects in the design process is the calibration of the load condition factor γc for asymmetric response from variation in soil resistance, establishing of maximum distance between the buckles and finally performing the seabed intervention design in order to fulfill the design criteria. The finite element model is also discussed in general and the pipe-soil resistance in particular.