System Reliability for Jacket Platform Subjected to Wave and Current Loads

Abstract—Codes applicable to Jacket platforms such as API
WSD, API LRFD and ISO 19902, are based on component and
joint reliability design. They consider overall structural
integrity, redundancy and multiple failure paths only indirectly
by using structural integrity assessment methods. Failure of a
single component does not mean that the capacity of platform
has reached the limit and hence for the reassessment of old
platforms component based approach becomes unviable. So
instead of component reliability, system reliability analysis
method is used to check the reserve strength of the platform and
find its redundancy. In this study, the maximum wave height is
increased corresponding to applied wave load and base shear of
platform is obtained using SACS analysis. Regression analysis is
used to find the constants for load equation by converting the
wave and currents forces into environmental load model by the
use of curve fit tool of Matlab. Probabilities of failure, return
periods, safety indices and their COV are obtained against an
RSR of 1.5-2.5. Finally target probability of failure is compared
with achieved failure probability.
Keywords— Reserve strength ratio, Base shear, Return periods,
Jacket Platform, Environmental loads.