Hybrid Simulation of a Structure-Pipe-Structure Interaction Within a Gas Processing Plant

Though often overlooked, the impact of seismic transient ground deformation on natural gas (NG) pipes can be highly adverse. Particularly, pipe elbows may undergo excessive in-plane bending demand and buckling. In this paper, a critical scenario of a pipe coupling two industrial structures typically found in an NG processing plant is studied. High strain and cross-sectional ovalization on the elbows are probable during an earthquake due to the out-of-phase oscillation of the two structures imposing asynchronous displacement demands at the two pipe-ends. A parametric study was first performed to investigate various structure-pipe-structure configurations which increase seismic demands to pipe elbows. Simultaneous mobilisation of divergent oscillation between two supporting structures at the low-frequency range, a lower pipe-structure stiffness ratio, a shorter length of straight pipe segments in the linking pipe element and a higher pipe internal pressure have led to the onset of critical strain demands in pipe elbows. To validate this observation, an experimental campaign was developed where a full-scale linking pipe element was physically tested by means of hybrid simulation (HS). The study shows that the seismic interaction of the structures coupled with the pipe is non-negligible and can be even critical for the integrity of the coupling pipe. The finding depends on the structural system’s dynamic and geometrical properties as well the frequency content of the earthquake excitation.