Cyclic Deformability of Steel Pipes With Local Metal Loss and Repaired Pipes

Cyclic deformability of steel pipes with local metal loss was studied. Full-scale tests were conducted using X42 and X52 pipes with diameters of 762.0 to 609.6mm. Each test pipe specimen contained an artificial metal loss of rectangular shape and uniform depth on the external surface, and inner pressure and cyclic axial strains were applied with constant amplitudes up to 7 cycles. Buckling deformation was observed in the metal loss region during compressive loading, and it induced a load reduction. The experimental results were analyzed by cyclic elastoplastic FE analysis. The effectiveness of the FE analysis was validated and parametric studies were performed. Buckling was strongly affected by the dimensions of the defect. Through these experiments and FE analyses, we suggested fitness-for-service criteria for buried pipes with external metal loss, taking into account large ground movement during strong earthquakes. Similarly, we examined the aseismic performance of three repair methods for the metal loss region—patch-welding, full-encirclement hot sleeve and weld deposition—through full-scale tests using X42 and X52 pipes with a 609.6mm diameter. We found that patch-welding and weld deposition performed sufficiently well, while the sleeve on the pipe induced buckling near the circumferential fillet weld due to constraint in the radial direction.