Experimental Results of Steel Lap Welded Pipe Joints in Seismic Conditions

Welded lap joints are commonly used in large-diameter steel pipelines for water transmission. Their structural performance constitutes a key issue for safeguarding pipeline structural integrity with no loss of pressure containment, required even after a severe seismic event. Full-scale experiments are presented herein, and are part of an extensive project sponsored and coordinated by Northwest Pipe Co. on the structural performance of welded lap joints under severe ground-induced (seismic) actions. In the companion paper “Numerical Simulation of Steel Lap Welded Pipe Joint Behavior in Seismic Conditions” numerical simulation of the experiments are presented. The paper describes a series of large-scale experiments on welded lap joints in 25.75 in outside diameter steel pipes, with wall thickness of 0.135 in (3 specimens) or 0.250 in (3 specimens). The specimens were internally pressurized to 40% of yield pressure, and then subjected to four-point bending. Measurements of the bending load, characteristic displacements, and local strains at the joint area are reported. In all tests, the welded lap joints tested were capable of sustaining remarkable bending deformation, without any loss of pressure containment. This behavior supports the argument that welded lap joints, if appropriately constructed, can be used in seismic areas where severe and permanent ground-induced actions in the pipeline may occur.