Dynamics of Pipeline Spans Created by ZRB Buckle Triggers

Analytical Approximation

Abstract

Zero-Radius Bend (ZRB) buckle triggers provide a reliable means to accommodate thermal expansion of pipelines by triggering sufficiently closely spaced lateral buckles so that none of the buckles ends up absorbing too much thermal expansion.  However, it also creates a span to each side of the ZRB support, which may grow due to scour.  The same Rayleigh-Ritz approximation that has been successful in accounting for arch action for the first vertical mode of a single span is used to account for lateral arch action for a ZRB span affected by the lateral buckle that forms on the ZRB support.  The accuracy of the results for the first horizontal mode is compared with that from FE analysis.  It is found that the frictional axial resistance at the ZRB support has an important influence on the natural frequency and damping ratio.