Corrosion assessment and burst pressure prediction of line pipes with corrosion defects are essential for the integrity assessment of steel transmission pipelines. The failure assessment methods proposed in codes or handbooks may be overly conservative or exhibit significant scatter in their predictions. In this paper, the effects of two key parameters—the flow stress and Folias bulging factor, on predicting the failure pressure of pipelines with defects are studied. The Folias bulging factor is suggested by fitting the results from finite element (FE) analysis. Then, a new prediction method for the failure pressure of pipelines with defects is proposed. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods such as B31G, MB31G, Det Norske Veritas (DNV), and rectangular parabolic area (RPA).

Evaluating the burst pressure of corrosion cluster defects necessitates considering the interaction of contiguous defects. The importance of this interaction cannot be emphasized enough, as it plays a crucial role in determining the failure pressure of such pipelines. Current methods for assessing the failure pressure of corrosion cluster defects have drawbacks, including complex evaluation procedures and limited applicability. In this research, the failure mode and location of corrosion clusters with two or more defects are studied with a burst experiment on a full-scaled pipeline. Based on the failure position of the corrosion cluster, a “center failure location” method is proposed to estimate the burst pressure of colony corrosion defects. The method takes the defect in the failure position as the center; the influence of contiguous defects that interact with the central defect on its failure pressure is considered, and subsequently, the burst pressure of colony corrosion centered on the failure location is evaluated. In contrast with the current assessment methods, while the proposed approach does not reduce prediction errors, it requires fewer evaluation conditions and is operationally simpler and more versatile.

Double-layer pipelines are widely used in deep-sea energy transport because of their strong thermal insulation and enhanced structural safety. The stress distribution and the interaction mechanism between inter-pipes of double-layer pipelines are elucidated. A mechanical model is developed to characterize the thermal deformation difference between the two layers. The mechanical response of the pipeline can be divided into two distinct modes based on the initial deformation stages: (1) an inner-pipe-dominated elongation that creates compressive stress in the inner pipe and tensile stress in the outer pipe, and (2) an outer-pipe-dominated elongation that reverses this stress distribution. Sagging deformation (bowl-shaped deformation), primarily caused by the self-weight of the inner pipe, is identified as the critical factor that drives the stress concentration and bending moment at the inner–outer pipe connection. Engineering approaches, such as inserting spacers or additional supports in the annular cavity, effectively reduce peak stresses in both layers under extreme conditions.

In deepwater oil and gas transportation, Pipe-in-Pipe (PIP) systems are an effective solution for mitigating external loads while preserving internal thermal integrity. A finite element model with ITT elements and nonlinear spring contacts was developed in ABAQUS to simulate thermal expansion and contraction under extreme conditions. The coupled mechanical response of double-layer pipelines under non-uniform temperature fields and internal pressure was analyzed, focusing on stress distribution and deformation coordination between the inner and outer pipes. The inner pipe primarily sustains compressive or tensile stress depending on the thermal load direction, while the outer pipe experiences opposing stresses due to mechanical coupling. Distinct stress transfer zones are present near the pipe ends, governed by pipe-soil interaction and internal bending moments. The proposed model for double-layer pipelines under coupled thermal and internal pressure loads demonstrates a prediction accuracy within 5% as compared with benchmark numerical solutions. The simulations capture axial stress variations of up to 68% between extreme thermal expansion and contraction scenarios, with radial deformation ranging from 0.9 mm to 3.4 mm. These findings provide valuable insights into the safe and efficient design of subsea PIP systems, particularly for optimizing material selection and structural configuration in high-temperature, high-pressure environments.

Underground pipelines are the lifeline of the city. Steel pipes are widely used in water supply engineering, the wall thickness of the pipe will reduce due to corrosion and other reasons, resulting in a decrease in the bearing capacity. To clarify the mechanical properties of the pipe under the case of circular corrosion, a three-dimensional finite element model is established using ABAQUS, the influence of the mesh size on the convergence of the results is analyzed, and the finite element results were checked and evaluated using the analytical solution. Afterward, the effects of parameters such as corrosion diameter, corrosion depth, pipe diameter, and internal pressure on the maximum stress and displacement are studied. At last, based on 420 sets of data, the prediction equation of the pipe maximum stress is obtained. The results show that the finite element results are in good agreement with the analytical results, and the radial displacement of the corroded area is large. In corrosive areas, there are significant differences in stress at different locations. The radial displacement of the corroded area is significant, and the uncorroded area is almost unaffected. This study can provide a reference for the evaluation of the service performance of corroded steel pipes.