Experimental investigation of pipes with flexible joints under fault rupture

Objective of the present study is the experimental investigation and comparison of the response of continuous pipes and pipes with internal flexible joints under imposed transverse displacement, modeling seismic fault rupture. Three-point bending tests were performed modeling the deformation of buried pipes subjected to fault offset. The introduction of flexible joints between adjacent pipeline parts is proposed as an alternative protection measure to reduce developing strains due to such offsets. Indeed, experimental results confirmed very significant contribution of flexible joints in strain reduction, thus providing strong promise of effective protection of buried pipes from the principal failure modes occurring in such cases, i.e. local buckling of pipe wall and tensile fracture of girth welds between adjacent pipeline segments. Experimental results have been sufficiently reproduced by numerical simulation accounting for geometric and material nonlinearities and incorporating longitudinal residual stresses due to seam weld. The numerical analyses and corresponding results are also presented in detail.