Session: SE-08-01 Multi-Hazards and Margins

Paper Number: 62273

Start Time: Wednesday, July 14, 2021, 05:00 PM

62273 - Mechanical Response of an Industrial Piping System Under Strong Cyclic Loading 

In the case of severe seismic action, piping systems may be loaded well into the plastic range under large amplitude reversible cyclic loading. In particular, piping components deform into the inelastic range and fatigue-ratcheting may occur, causing failure of pressurized piping system. In recent years, significant research has been published aimed at improving the seismic design of the piping system, mainly motivated by the safety requirements of the nuclear industry. Towards this purpose, a series of experimental programs has been reported in the past on the assessment of the piping system under severe static or dynamic loadings that simulates the earthquake loading conditions.

In the present work, an experimental study is presented first, which examines the response of a pressurized three-elbow piping system subjected to reverse cyclic loading, supported by numerical simulations. The experimental work refers to an 8-inch-diameter piping system with nominal thickness equal to 6.35 mm (SCH20), containing three long-radius elbows and straight parts. It is pressurized first with internal pressure of 30 bar, and it is subjected to severe cyclic loading in a quasi-static manner. The piping system failed at flank region of one elbow, due to low-cycle fatigue

The second part of the investigation refers to the numerical simulation of the piping system response, for the purpose of elucidating some special issues, complementing the experimental work. A finite element model has been developed in ABAQUS, which employs the geometry of the specimens based on measurements conducted prior the execution of the experiment. The support conditions have been imposed in the numerical model exactly as in the experimental set-up, using appropriate kinematic constraints. A built-in constitutive model, proposed by Chaboche (1986), is employed for modelling the material behavior.

The numerical results are in good agreement with the experimental data and observations. Special issues such as strain ratcheting, and progressive pipe ovalization are discussed in detail. It is the authors’ opinion that the present experiment, and its simulation, can be used as benchmark for future research work on cyclic loading and ratcheting in piping components and systems.

Presenting Author: Giannoula Chatzopoulou University of Thessaly

Authors:

Charalampos Karvelas National Technical University of Athens
Giannoula Chatzopoulou University of Thessaly
Nikolaos Stathas University of Patras
Elias Strepelias University of Patras
Xenofon Palios University of Patras
Anna Zervaki University of Thessaly
Stathis Bousias University of Patras
Spyros A. Karamanos University of Thessaly