Session: DA-02-01 Design and Analysis of Piping and Components - 1

Paper Number: 83681

83681 - Overview of Piping Stress Analysis Using Shell Elements 

Shell elements provide a more realistic finite element model of a piping system than beam elements.  However, stress analysis of piping systems is still performed almost exclusively using beam elements in a linear elastic analysis. This is understandable given that most of the widely used piping codes such as ASME B31.3 are set up for beam modelling.  Piping codes make use of stress intensification factors (SIFs or i-factors) to amplify stresses at complex geometries in beam models in order to provide a simple method to assess a particular piping system against code stress limits.  The price paid for the convenience of stress intensification factors is often a conservative analysis as more accurate results would be obtained with shell modelling. 

Historically, computational limitations have meant that beam modelling is often the only engineering tool available to assess piping systems – even for cases where it may provide unsatisfactory results. Recent improvements in computing power and software packages mean shell modelling can now be viewed as a realistic option for cases where beam modelling may be inadequate. 

This paper will provide an overview of shell modelling to assess piping systems compared to traditional beam modelling.  A number of examples will be presented illustrating the benefits of analysing a piping system using shell elements.     These include pipes with large diameter to thickness ratios and cases where use of the material’s true stress-strain curve is desirable. It will be shown how beam models can also benefit from shell modelling to improve accuracy.  Some of the challenges and disadvantages of using shell elements will be discussed including aspects requiring consideration and awareness on the part of the analyst.  Recommendations and suggestions for using shell elements to model piping are put forward. 

Presenting Author: Robert Weyer Amesk

Presenting Author Biography: Robert Weyer has worked in LNG plant piping since 2013 on two of the recent Australian LNG mega projects. He was the client technical authority for onshore piping and pipeline on Chevron’s Wheatstone project, followed by a short stint as lead piping engineer on Inpex’s Ichthys project. He holds a Master’s degree in Mechanical Engineering and is a Chartered Professional Engineer with Engineers Australia. Currently based in Perth, he is actively involved in LNG piping and provides specialist technical support through his consultancy, Amesk.

Authors:

Robert Weyer Amesk
Milad Hajimohammadkarim Energy Industries Engineering & Design Co. (EIED)