Pipeline repair plays an important role in safe pipeline operation. Composite material repair technology has been widely used in pipeline repair due to its advantage of light weight and low cost. In this paper, the failure loads of repaired pipe with composite under tension and internal pressure are analysed by experiments, Finite Element Method (FEM) and theoretical method, and simple formula of failure loads is obtained based on theoretical analysis and verified by FEM and experiments. First, the tension experiment shows that debonding happens in the repaired pipe before its fracture, and then the debonding details are showed in FEM results considering the adhesive debonding criteria, finally a simple formula expression is obtained for the failure tension loads based on the analysis of interface stresses, and the results are almost consistent with the experimental method and FEM. Similarly, for the case under internal pressure, the blasting failure loads are obtained for the repaired pipe based on the theoretical analysis, which are consistent with FEM results.

The umbilical is one of the most important components of a subsea production system. Processing errors and environmental load deviations may occur during the manufacturing process, and the deterministic design based on safety factors is often unable to meet the needs of engineering. In the present paper, the random distribution law of the umbilical geometry parameters is considered to analyse the reliability of the umbilical under the ultimate tensile load by combining the response surface approach of reliability analysis with the finite element analysis.

Corroded pipelines are often repaired with Carbon Fibre-Reinforced Polymers (CFRPs) because of their low cost, fast and easy process. In this paper, the Finite Element Method (FEM) was used to establish the model of corroded pipelines repaired with CFRP under bending loads. The progressive damage subroutine was used to simulate the damage of CFRP, and the cohesive element was used to simulate the damage to the interface. The failure modes of repaired and unrepaired pipelines were in good agreement with the experimental results. It was found that the failure order of CFRP and adhesive was different when the thickness of the adhesive changed. Failure competition existed between CFRP and adhesive, which led to different ultimate loads of the repaired pipelines. This research reveals that the failure modes and ultimate loads are relevant to the competition mechanism of different materials in composite structures.

Today, adhesive pipe joints are widely used in marine engineering equipment such as platforms and pipe lines, because of the manifest advantages, such as lower stress concentration, uniform stress distribution, lighter weight, water tightness, corrosion-resistance and better fatigue properties. However, adhesive joints in riser pipes are the most vulnerable part where most failures occur, because singular stress fields exist at the extremes of the interface between the adhesive and the adherend. In order to prevent premature failure of the joint systems, a study of adhesive pipe joints under the actual sea environment loadings, including as external pressure, internal pressure, tension, torsion, bending, and combinations of these, should be conducted. In this reported study, stress distributions were analysed in terms of the first-order laminated theory, and it was found that numerical results were in a good agreement with the obtained results obtained from the finite element analysis. In the light of these results, the failure of adhesive joints in deep sea riser pipes was discussed based on stress distributions on the interfaces as defined by theoretical analysis and Finite Element Method. Moreover, the effects of material properties and joint dimensions on the strength of adhesive joints under different load cases were studied.