Testing and Analysis of Steel Pipes under Bending, Tension, and Internal Pressure

This paper reports a full-scale experimental program consisting of six pipe specimens made of X65 material (specified minimum yield strength=448 MPa) with 508 mm outer diameter, and a diameter-to-thickness ratio (D/t) of 81.2 subjected to combinations of bending, axial tension, and internal pressure. The study is aimed at determining whether the pipes are able to attain their modified plastic moment as predicted by analytically derived plastic interaction relations. The moment versus curvature relations, peak moment values, and local buckling behavior of the specimens as obtained from the experiments are documented. The peak moments obtained are compared to the analytically predicted moments. A nonlinear shell finite-element model is also developed using the finite-element analysis (FEA) simulator ABAQUS in order to predict the moment capacity and the local buckling behavior. Test results compare well with FEA results. It is observed that under certain combinations of axial tension and internal pressure, pipes with D/t=81.2 are able to attain their plastic moment resistances.