Mechanical Behavior of Corroded Steel Pipe Rehabilitated by Liner Under Four-Point Bending

Abstract During operation, buried pipelines are vulnerable to corrosion induced by electrochemical factors, microorganisms, and stray currents, leading to compromised structural integrity and diminished load-bearing capacity. Cured-In-Place-Pipe (CIPP), a trenchless, environmentally sustainable, and highly efficient rehabilitation technique, has gained widespread adoption for pipeline repairs. This study develops a three-dimensional finite element model to simulate a corroded pressure pipeline rehabilitated with CIPP, subjected to four-point bending loads. The model is validated against experimental data. The effects of internal pressure, liner thickness, elastic modulus of the liner, corrosion depth, corrosion length, and corrosion width on the pipeline's bending strength and stress distribution within the liner are thoroughly examined. The results reveal that increasing internal pressure diminishes the bending strength of the pipeline. Specifically, when internal pressure reaches 40% of the yield pressure, the maximum circumferential stress in the liner shifts from the invert to the crown. Enhancing the liner thickness progressively improves bending strength. Specifically, for the baseline model in this study, a 1 mm increase in liner thickness resulted in an average increase of 2.43% in yield load and 6.09% in ultimate load. However, these values are specific to the investigated case and may vary with pipe dimensions, material properties, and defect characteristics. Some of the highlights are as follows: (1) A three-dimensional finite element model is developed. (2) The model is validated against experimental data. (3) The influence of each parameter is analyzed. (4) For each 1-mm increase in liner thickness, the ultimate strength rises by 6.09%.