Response of Bell‐Spigot Jointed Ductile Iron Pipelines Under Different Normal Fault‐Pipe Crossing Positions: Full‐Scale Experiment and Analytical Solution

ABSTRACT Seismic faulting can cause severe damage to buried ductile iron (DI) pipelines. Existing studies consider the scenarios of fault‐pipe crossing at a pipe joint or the middle of a pipe segment only. Moreover, there is a lack of analytical assessment methods for maximum joint rotation under normal faults. In this study, full‐scale experiments are conducted to analyse the influence of fault‐pipe crossing position on the behaviour of DI pipelines under 90° normal faulting. New tape optical fibres and linear potentiometers under an improved instrumentation scheme are employed to monitor the pipe strains and joint kinematics. The results indicate that as the fault‐pipe crossing position, rp , shifts from the joint ( rp = 0) to three‐quarters of the pipe barrel length ( rp = 0.75), the pipe‐soil interaction mechanism changes from the uplift capacity‐controlled mode to the bearing capacity‐controlled mode. In terms of joint kinematics (maximum joint rotation and axial displacement) and maximum bending strain, the most unfavourable fault‐pipe crossing positions are rp = 0∼0.25 and 0.75, respectively. The joint rotation near the fault trace should be prioritized to avoid the loss of DI pipe serviceability. An analytical model that enables safe evaluation of peak joint rotation under normal faulting is proposed.