A Novel Onshore Full-Scale Lateral Buckling Test Concept: Design, Commissioning, and First Results

Abstract Lateral buckling (LB) is a critical failure mode for flexible offshore pipelines, particularly in deep water environments. Replicating the complex offshore conditions required for LB is extremely costly and logistically challenging. This work presents the development of an onshore, instrumented LB test rig that mimics the full-scale offshore conditions and failure modes observed in deep immersion performance (DIP) tests. The test rig is designed to reproduce the boundary conditions, axial loading, and repeated bending experienced by flexible pipelines in LB-relevant scenarios. The test is conducted on 22-m pipe samples to accurately reproduce the touchdown zone dynamic behavior and curvature development, as well as averting fixation effects from the pipe ends. The axial loading is applied mechanically, and the pipe is thoroughly instrumented including LiDAR-based curvature measurements. Many other onshore LB tests depend on large hyperbaric chambers, making them costly, allowing for shorter pipe samples, and complicating the instrumentation. Tests in hyperbaric chambers also require test end fittings (EFs) with sealing systems, while the test concept developed in the present work provides a cost-effective and practical alternative. Results are presented demonstrating the ability to replicate LB failures for 8-in. pipes and the induced tensile armor (TA) deformation is examined using structured light 3D scanning. The work represents ongoing efforts toward a qualified and instrumented laboratory LB test representative of flooded or breached outer sheath (OS), also known as “wet” annulus, conditions to complement DIP tests. Some calculations are necessary to translate polymeric layer behavior to pressurized conditions, but the validated test setup represents an advancement in the assessment of LB for offshore flexible pipeline design and LB performance predictions.