Future offshore pipelines development moves towards challenging operating condition and deep/ultra-deep water applications. Understanding the failure mechanisms and quantifying the strength and deformation capacity of pipelines, special components (buckle arrestors, wye, etc.) and in-line structures (in-line sled, in-line valve, in-line tee, etc.) is a need, under installation and operation loads, taking in account different geometrical characteristics and mechanical behaviors. The objective of this paper is to present and discuss recent FEM approaches integrating global and local analyses to evaluate the pipeline response and local effects, respectively. Thanks to this method the results coming from the global FEM analysis (main loads and driving phenomena) are used as input data for local FE Model with the aim to detect stress/strain intensification and other issues due to the local characteristics. In this paper: • The challenges of future deep water offshore pipelines are briefly presented; • The typical loading scenarios for pipelines during installation and operation are discussed; • The PipeONE 2014 tool, developed to facilitate the input/output data sharing between global and local FEM analyses, is presented and fully described in its main characteristics and capabilities; • An example is presented with the aim to understand and to appreciate the PipeONE 2014 functionality in FE modeling.

There is consensus on the need for in-service buckling analyses to assess the integrity of both flowlines and long distance trunklines subject to HP/HT service condition. The extent of the analyses and supporting survey depends on the severity of the application. In the last two decades, the pipeline industry has gained significant experience in both the design and operation of pipeline systems exposed to global buckling. Actually, the early 90s have been a watershed: before the phenomenon was just known (theoretically), then it was seen...as soon as pipeline integrity management programmes have been introduced in the offshore pipeline industry practices. Although, limited information have been documented in the open literature, now as then. Several efforts have been dedicated to develop design methods and procedures suitable for operating pipeline safely as well as protecting the population, environmental resources and assets. At the beginning, there was a gap to be closed as specific mitigation measures were never designed. Nowadays, thanks to computational progress, it seems that the attention is addressed to face the uncertainties affecting the subject matter but, sometime, leading to overdesign. The scope of the paper is to present aspects of global buckling design analyses that were performed in recent projects with the aim to highlight the challenges and the risks, the accuracy or the limitation of the methods, the feedback and the lesson learnt of real installed pipelines under operating conditions.

Concrete Weight Coating is used in offshore industry to provide for pipeline vertical and lateral stability against waves and currents and to guarantee protection against fishing activities. Reinforced concrete coating of adequate strength, especially in case of thick coatings for stringent in-place stability requirements, entails additional bending stiffness and consequently strain concentration at field joints, thus significantly affecting the state of stress and strain on the pipe steel during laying firstly, and then during operations. Attention of the offshore pipeline industry has been focused in the development of experimental and theoretical activities in a more scientific way, which aimed to satisfy the need of a better knowledge in this field. Both analytical and FEM solutions are available in the free literature and relevant standards to predict the contribution of concrete coating layer on global pipeline strength and deformation capacity and simplified threshold values for the concrete damage are provided, as well. Generally, for installation analysis purpose, a pipeline with equivalent mechanical behavior (bending moment-curvature relationship) and physical (weight) properties is used in installation and operation analyses. No assumptions are typically made on concrete damage evolution to evaluate the decay of pipe capacity beyond the elastic range. In this paper new advances in modelling the mechanical behavior of concrete coated joints are discussed. In particular an advanced ABAQUS finite element model is proposed to take into account the effect of concrete coating damage on the overall capacity. The following effects have been accounted: • Non-linear stress-strain relationship of the steel at large usage factors/curvatures on the strain concentration at the field joint. • Concrete coating damage evolution on global pipeline bending stiffness. In this paper: • The state-of-the-art about published materials, numerical studies and design approaches on concrete material modelling and concrete coated pipes is briefly presented; • A FEM based analysis methodology is drawn and proposed for the strength and deformation capacity assessment of a concrete coated pipe; • The FEM model is calibrated on available full scale tests; • The results of a project case study performed with ABAQUS FE Model are given.