Implications of Inspection Updating on System Fatigue Reliability of Offshore Structures

Abstract

Offshore structures are considered as fail safe and inspections are carried out during their service lifetime to assess their actual condition. In this paper, the effect of inspection updating on fatigue reliability of offshore structures is investigated. In particular, the effect of inspection on the reliability of both inspected and uninspected joints is assessed dependent upon the correlation of properties of different joints. The effect of repeated inspections and inspection sample size on fatigue reliability is also investigated. The influence of inspection of certain joints on the reliability of a series system is studied and the effect of system-based updating policy on fatigue reliability is investigated. It is found that the system reliability is significantly affected by the inspection updating policy. [S0892-7219(00)00403-9]

Effect of different inspection strategies on the reliability of Daniels systems subjected to fatigue

“…These values are in accordance with Moan and Song (2000). Table 1 also lists the value of the PoD parameter (see Equation (14)), which is selected so that the PoD model is representative for magnetic particle inspection; see (Moan et al 2000a).…”

“…Finally, the correction factors and are fully correlated among all elements. This approach is based on a correlation model suggested in Moan and Song (2000).…”

“…Moan and Song (2000). Straub and Faber (2005) present a risk-based method for planning inspections on system level taking into account stochastic dependence among element deterioration behavior.…”

Reliability-based inspection planning in view of both crack initiation and propagation

“…The POD curve for an inspection method is obtained from blind-tests or inservice inspection data. In this paper, the PoDs for CVI and MPI are modelled with the commonly-used exponential distribution (Chen et al, 2011, Moan andSong, 2000). The PoD (also the cumulative probability function for variable ) is given by = ( ) = 1 − exp(− ⁄ ) (16) where is the mean detectable crack size.…”

Probabilistic fatigue life updating accounting for inspections of multiple critical locations

“…Sørensen and Ersdal [23] have shown that a high degree of correlation between the uncertain parameters in different components is needed in order to obtain substantial information which can be used in inspection planning. Moan and Song [24] have studied the influence of inspection updating on the fatigue failure probability of a series system. Uraga and Moan [25] have considered the fatigue reliability of a parallel system consisting of 2 joints.…”