Improving the Performance of Steel Pipe Welded Lap Joints in Geohazard Areas

Abstract

Finite element simulation of the structural performance of stiffened lap welded pipeline joints was performed, subjected to severe axial and bending loading conditions, resulting from ground-induced actions, in the presence of internal pressure. The pipe, the welded lap joint and its reinforcement were modelled in FE program ABAQUS with shell and solid finite elements, accounting for geometric nonlinearities, such as large deformations and buckling, as well as the nonlinear behavior of steel pipe material beyond the elastic regime. This paper describes the joint assembly, the resultant benefits shown in the FE modelling to the seismic resilience with the added joint strength, as well as the parameters required for specifying the stiffened joint in design. FE Results are presented for lap welded joints (unstiffened and stiffened) in a steel pipe with diameter-to-thickness ratio of the parent pipe equal to 180, subjected to axial loading, longitudinal bending, and internal pressure. Lap joints with double welds are considered on the inside of the joint, the outside of the joint and on both sides of the stiffened joint. For each loading case, the load-deformation relationship is determined, and local strains are measured in critical locations for different levels of loading. Local buckling (bulging) under compression is simulated explicitly through the finite element solution, whereas the possibility of tensile failure is detected through monitoring the value of the maximum tensile strain. The numerical results focus on the mechanical behaviour of a 66-inch-nominal-diameter pipe with 0.37-inch thickness, and refer to both global structural response and the evolution of local strains in critical locations. At the time of drafting this paper, HDR, Inc. is preparing to conduct a physical testing of the stiffened joint to affirm the performance and define the manufacturing requirements. © 2016 ASCE.