Newly Developed Seismic Resilient Steel Pipe Joint Safeguards: Pipeline Structural Integrity during Severe Geohazard Events

The mechanical performance of lap welded joints is essential for safeguarding the structural integrity of steel water pipelines, after a severe earthquake or other geohazard loadings. Over the past 4 years, an extensive experimental project was launched to determine the structural performance of lap welded joints under the most severe ground deformations. The research consisted of full-scale physical experiments, supported, and validated by rigorous numerical finite element simulations. The experimental results have indicated a remarkable strength and deformation capacity of the standard lap welded joints without loss of water containment. In addition questions related to local lap weld joint deformation were elucidated and the corresponding strains developed under extreme tensile or compressive loads at critical locations were quantified, demonstrating the ability of those joints to sustain a significant amount of local strain at critical locations. The latest phase of the research focuses on the behavior, analysis, and design of a new seismic resistant lap welded joint. Results of a series of additional full-scale experiments, supported by finite element numerical simulations, on the mechanical performance of the new lap welded joints under severe structural (axial and bending) loading conditions are presented herein. The new lap weld joint comprises the standard lap weld configuration but contains a small geometric projection introduced at a specific location near the field applied fillet weld. Based on current research results, a modification of the standard lap welded joint is proven to result in consistent buckling of the steel pipe cylinder and not the lap weld joint, during severe or extreme loading. The proposed joint, referred to as “Atlas Seismic Resilient or ATLAS SR-joint”, effectively allows steel pipe to not be limited by the capacity of the standard lap welded joint during strong seismic or geohazard events, and offers an efficient, reliable, yet economical solution for welded joints in steel water pipelines in geohazard areas.