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.