Aglaia E. Pournara

Structural Integrity of Buckled Steel Pipes

Local distortions on steel pipeline wall in the form of buckles may constitute a threat for the structural integrity of the steel pipeline. In the present paper, experimental research supported by numerical simulation is reported to investigate the structural integrity of buckled steel pipes. A series of six (6) full-scale experiments has been carried out on 6-inch X52 pipes, followed by finite element simulations. The buckled steel pipes are subjected to cyclic loading (bending or pressure) in order to estimate their residual strength and remaining fatigue life. The finite element analysis simulates the experimental procedure for each type of deformation and loading case, in order to estimate the local strain distributions at the buckled region. Based on the numerical results, fatigue life is predicted and compared with the experimental results using an appropriate defined damage factor. The results of the present study are aimed at evaluating existing guidelines and methodologies towards appropriate assessment of local wall distortions in steel pipelines.Copyright

STRUCTURAL INTEGRITY OF STEEL HYDROCARBON PIPELINES WITH LOCAL WALL DISTORTIONS

Local distortions on pipeline wall in the form of dents or buckles may constitutea threat for the structural integrity of the steel pipeline. In the present paper, experimental research supported by numerical simulationis reported to investigate the structural integrity of smoothly dented steel pipes. A series of six (6) full-scale experiments on 6-inch X52 pipes has been carried out, and numerical simulations have also been conducted.The dented steel pipesare subjected to cyclic loading (bending or pressure) in order to estimate their residual strength and remaining fatigue life. The finite element analysis simulate the experimental procedure for each type of deformation and loading case, in order to estimate the local stress and strain distributions at the dented region. Based on the numerical results, fatigue life is predicted and compared with the experimental results. The results of the present study are aimed at evaluating existing guidelines and methodologies towards appropriate assessment of local wall distortions in steel pipelines.

Strength and stability of High-Strength Steel tubular beam-columns

The present work examines structural strength and s tability issues for steel tubular beamcolumns made of high-strength steel. The tubular be m-column elements are widely used in a variety of structures such as buildings, off-s hore templates, masts, towers and cranes. The research focuses on the analysis of such member s for better understanding the benefits of using high strength steel in tubular structures. Extensive numerical work has been conducted on CHS high strength steel beam-columns of two cross sections and various values of member length. First, considering initial out-ofstraightness imperfection, structural member stabil i y curves are calculated. Subsequently, an extensive beam-column analysis takes place and i nteraction diagrams are provided as a result. The numerical results are compared with the predictions of the current Eurocode 3 provisions.

MECHANICAL BEHAVIOR OF STEEL PIPES WITH LOCAL WALL DISTORTIONS UNDER CYCLIC LOADING

Evaluating the severity of pipe wall distortions is a crucial step towards safeguarding the structural integrity of aging hydrocarbon pipeline infrastructure. The present research refers to the remaining life of oil and gas transmission steel pipelines with local wall distortions (i.e. dents and buckles) under repeated loading. The research described in this paper constitutes the first part of a large numerical/experimental research project, aimed at developing methodologies and relevant design guidelines towards assessing and repairing structural pipeline damages in the form of local wall distortions. The paper describes numerical research aimed at investigating the residual structural integrity of smooth dented and buckled steel pipes, with respect to repeated loading that causes fatigue, with the purpose of designing large-scale experiments. Finite element models are developed to simulate the formation of dents and buckles on the pipe wall at various sizes (depths). The deformed steel pipes are further subjected to cyclic pressure or cyclic bending loading in order to estimate the remaining fatigue life of the deformed pipe. The local stress and strain variations due to cyclic loading application are calculated numerically at the deformed area of the pipe wall. In addition, the local strain variations are expressed in terms of strain concentration factors (SNCF) at the critical region of the pipe.