Finite Element Analysis for Piping & Vessel Engineers using CAESAR II

Transcription

1 Finite Element Analysis for Piping & Vessel Engineers using CAESAR II Experienced stress engineers know that beam element programs like CAESAR II have limitations that, for certain types of problems, may indicate a stress or loading problem that doesn't exist, or fail to indicate one that does. The typical scenario is one where larger diameter pipes and their intersections are inadequately modeled by beam theory. There are also errors and limitations in our existing piping codes that engineers sometimes need to address. Stress intensification factors given by the code are limited and sometimes wrong. This is not news. When we attach a pipe or structural support to a bend, what's the SIF supposed to be? Piping codes don't address these and many other geometries that we build in practice every day. For these and other problems, finite element analysis (FEA) is the answer, but the ability to build FEA models, generate good results and relate the results to meaningful piping code stresses and allowables requires expertise or time that most stress engineers don't have. FEATools is a unique collection of FEA software applications specifically developed to solve piping & vessel problems that beam element and current code limitations prevent you from solving accurately. Why is this important? Take the large diameter pipe issue - in many cases, stresses and loads are calculated and reported to be much higher in beam analysis programs when compared to reality. With larger pipe, the solutions to problems that don't exist cost a lot more than solutions to smaller-bore piping problems (where beam theory provides more accurate answers). The result is that many engineers re-route pipe or otherwise spend a lot of money solving problems that don't really exist. Wouldn't it be nice to click a button & get a better answer? That's exactly what one of the utilities in the FEATools library does. You point to a CAESAR file, and FEATools reads the file, identifies the Tees, performs FE analysis, calculates flexibilities and SIFs, then create a new CAESAR model with these new properties in the model.

2 The results can be alarming, and it's so easy to do. To accomplish the same task in the past would require running FEA software separately, generate the new SIFs and flexibilities, then make elaborate modifications to the pipe stress model to reflect these changes; very time consuming. The technology at work in FEATools was developed over the last 22 years by Paulin Research Group (Tony Paulin being the original author of CAESAR II and a world leader in piping & vessel FEA research and code committee member/guru). For many reasons, every CAESAR II user should have FEATools on their desktop today. FEATools Main Menu:

3 Modules included: FE107 - FEA on fabricated branch connections: Unreinforced Tees, Pad-reinforced Tees and Laterals Stresses per ASME Section VIII, Division 2 with comparison to WRC 107 & WRC 297. FE-107 Screens FESIF - FEA on fabricated branch connections: Designed to calculate SIFs and stiffness values for use in CAESAR II. FEBend - FEA on bends with our without attachments, including piping and structural attachments. Generate SIFs stiffness and perform full stress evaluations. FEBend Screens FETee - FEA on contoured Tees. Extruded and B16.9 Tees included. Useful for evaluating non-compliant Tees. CAESAR II Enhanced Branch Connection Modeler - Use FEA or ST-LLC to apply more applicable data to a CAESAR II input file than beam-theory and code defaults. Automatically models FEA-evaluated SIFs and k's and creates a new CAESAR II model with the modifications. This feature alone is worth the price of admission. New Branch Connection SIFs and Ks - Display & compare SIF and stiffness factors from a wide variety of notable sources. Also calculates stresses for various combinations of loads. New Branch Connection SIF and Ks Screen.

4 FE-107 Input:

5 FE-107 Tabular Results:

6 FE-107 comparison of FEA vs. WRC 107/297 results:

7 FEBend Input dialog:

8 FEBend output graphics:

9 SIFs and Ks: