Asset integrity and management is an important part of the oil and gas industry especially for existing offshore structures. With declining oil price, the production rate is an important factor to be maintained that makes integrity of the structures one of the main concerns. Reliability based and risk-based inspection (RRBI) constitutes an efficient method to optimize inspection planning. Basing the inspection planning on pre-posterior Bayesian decision analysis and especially a Value of Information analysis allows to explicitly quantify the expected benefits, costs and risks associated with each inspection strategy. A simplified and generic risk-based inspection planning utilizing pre-posterior Bayesian decision analysis had been proposed by Faber et al. [1] and Straub [2]. This paper provides considerations on the theoretical background and a Value of Information analysis-based inspection planning. The paper will start out with a review of the state-of-art RBI planning procedure based on Bayesian decision theory and its application in offshore structure integrity management. An example of the Value of Information approach is illustrated and it is pointed to further research challenges.

This paper describes implementation and application of nonlinear lateral soil models for pipeline lateral buckling analysis. Several lateral soil models have been developed in the past and the model developed by Verley is often referenced in pipeline on-bottom hydrodynamic stability analyses (see [11], [13]). The Verley's model includes the build up of soil passive resistance as a function of small cyclic lateral motions and it is implemented in the PONDUS software (developed by MARINTEK) for on-bottom stability analysis as well as the DNV-RP-F109. However, the Verley model does not include the build up of additional soil berm resistance due to large cyclic in-place lateral motions applicable for lateral thermal buckling behaviors. The effect of additional soil berm resistance from large cyclic motions has been investigated by other research projects, such as the SAFEBUCK JIP [5]. In this paper, a complete non-linear lateral soil models with inherent soil berm resistance including both effects are formulated. The soil model combines the Verley model, the models described in DNV-RP-F109, and the berm model from SAFEBUCK's results. The DNV and Verley's model are used to model soil resistance in small amplitude cycle continued by the berm model after breakout achieved during large amplitude cycle. The new model is compared with PONDUS to validate the results of Verley and DNV model. The soil model is implemented inside SIMLA software [15] to enable finite element analysis. An example application of the model to pipeline global buckling analysis is then presented.

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Analysis of structures will in general involve large and complex numerical models, which require extensive computation efforts. These models are frequently referred to as digital twins. This analysis becomes particularly cumbersome for cases where a large number of response calculations are repeatedly performed, such as in the case of Monte Carlo simulation. One way of avoiding this will be to introduce simplified numerical models, which are no longer twins but some kind of more distant numerical relative. As an example of such a simplified numerical representation, a so-called response surface model can be applied in order to overcome the excessive computational efforts. Such models are also sometimes referred to as meta-models or cyber-physical models. One possible approach is to use a response surface model based on first-or second-order polynomials as approximating functions, with the function parameters being determined based on multivariate regression analysis techniques. In this chapter, various types of approximate models are first discussed in connection with a simplistic example. The application of response surface techniques is subsequently illustrated for a quite complex physicsbased structural model for an offshore jacket structure in combination with Monte Carlo simulation techniques.