Page 48 - Pipelines and Risers

Jn troduction 21

(1) Advanced Analysis for Design: to simulate pipeline in-place behavior during the following
through-life scenarios:

installation (Damsleth et al. (1999))
flooding, pressure test, dewatering, filling with product
pressure and temperature cycling due to operation and shutdowns
expansion, upheaval and lateral buckling (Nystrom et al. (1997), Tomes et al. (1998))
wave and current loads
on-bottom stability (Ose et al. (1999))
vortex-induced vibrations (Kristiansen et al. (1998), Reed et al. (2000))
trawlboard pullover and hooking (Tames et al. (1998))
effects of changes to the seabed

(2) Numerical Tool as Alternatives to Full Scale Tests: to develop design criteria with respect
to allowable span height and energy absorption capacity requirement from consideration of
protection of free-spanning pipeline against fishing gear impact loads and dropped objects
loads (Temes et al. (1998)).

Until some years ago, full-scale tests had been the only reliable method to determine strength.
These tests require large amount of resources and cost. Today, many full-scale tests may be
performed numerically using the finite element approach.

(3) Numerical Structural Laboratory for Limit-state Design: to develop design criteria with
respect to structural strength and material behavior as below:

- local bucklinglplastic collapse (Hauch and Bai (1998))
- bursting strength under load-controlled and displacement controlled situations
- ratcheting of ovalisation due to cyclic loads (Kristiansen et al. (1997))
- material non-homogeneity and computational welding mechanics

(4) Reliability-based Design: An example of reliability-based design is to select wall-
thickness, especially corrosion allowance based on reliability uncertainty analysis and LCC
(Life-Cycle Cost) optimization (Nadland et al. (1997a), (1997b)).

(5) Reliability-based Calibration of Safety Factors: to select partial safety factors used in the
LRFD (Load Resistance Factored Design) format by reliability-based calibrations (Bai et al.
(1997), Bai and Song (1997)).