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

Abstract

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 that increase seismic demands to pipe elbows. Simultaneous mobilization 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 in which 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 nonnegligible and can even be 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.