2009 - present (in progress)
The present research aims at estimating the residual structural capacity of oil and gas transmission steel pipelines, which contain defects in the form of wall wrinkling (i.e. local buckling). The necessity of inspection and examination of pipe wall deformations, caused by external forces, is crucial especially for old pipeline networks, in order to safeguard their structural integrity and the unhindered flow of energy resources. Numerical and experimental research are being carried out in order to investigate the residual structural integrity of buckled steel tubes. A non-linear numerical analysis is planned to be conducted in order to simulate the formation of local buckles (Figure 1& 3). Furthermore, a series of experiments on steel tubes will be carried out, where steel tubes of different geometries will be buckled first using the appropriate mechanical equipment, and subsequently, the deformed tubes will be subjected to further monotonic and cyclic loading in order to estimate their residual strength and remaining fatigue life. Numerical simulation of the experimental procedure will be conducted for each type of deformation and loading case in order to verify the experimental results and estimate the level of residual stress and strain distributions around the deformed area of the pipe wall.
The ultimate objective of this present research emphasizes on the utilization of the experimental and numerical results for the development of design guidelines and methodologies, which will be employed for the inspection, estimation and possible repair of hydrocarbon steel pipelines with structural damages in the form of wall wrinkles.
Figure 1: A locally-damaged pipeline with wall wrinkles (buckles).
Figure 2: A buckled pipeline segment, failed under cyclic loading due to fatigue [test at TU Delft].
Figure 3: Numerical simulation of buckled pipeline due to excessive bending.