STRUCTURAL INTEGRITY ASSESSMENT OF A NUCLEAR PIPING SYSTEM UNDER SEISMIC CONDITIONS

Abstract

Accurate modeling of pipe elbows is critical in seismic assessment of nuclear piping systems, as
curved sections exhibit amplified flexibility, ovalization, and nonlinear stress behavior compared
to straight pipes. This study evaluates the performance of ELBOW290 elements in ANSYS
Mechanical against detailed SHELL281 shell models for nonlinear seismic analysis.
A two-stage global–local methodology is adopted. The global piping system is analyzed using line
elements to extract seismic displacement histories, while a critical elbow is studied using both
ELBOW290 and SHELL281 elements. Material nonlinearities are modeled using Multilinear
Kinematic Hardening (global) and Chaboche Nonlinear Kinematic Hardening (local).
Results demonstrate that ELBOW290 accurately captures stress concentration, ratcheting, and
ovalization effects with less than 5% deviation from shell models while reducing computational
cost by approximately 86%. The study validates elbow element technology as a reliable and
efficient solution for seismic qualification of nuclear piping systems.