Inelastic Pipework Dynamics and Aseismic Design

Abstract

This paper shows a simple correlation between elastic and inelastic dynamic pipework responses enabling realistic/pessimistic prediction of dynamic pipework responses beyond the elastic range using current elastic aseismic design procedures. In this paper, theoretical studies relating dynamic responses directly to nonlinear material stress/strain characteristics show how such a correlation arises, particularly for materials exhibiting a well-defined yield point inflection, and the evaluation of the correlative parameters (moduli and damping factors). The ABAQUS computer program was used to study and simulate the dynamic inelastic response characteristics of a pressurized tube in the form of simple beam and a pressurized cantilevered elbow (in-plane responses). Using comparative dynamic test results for these components, the foregoing design concepts were verified for representative cyclic material characteristics. So, given appropriate cyclic material characteristics, pessimistic incremental and reverse cyclic fatigue strains may be simply evaluated for loadings beyond the elastic range (for assessment against ASME fatigue criteria) using existing design techniques as shown in the paper.