In 2009, ASME published that there are generally 3 methods used by most computer programs for stress analysis, 2 of which "General Straight forward Approach" and "Algebraic Subtraction Approach" (used by Caesar II) were found to produce inaccurate results. Only "Operating Condition Approach" used by programs like AutoPIPE, FE Pipe, Ansys, Abacus, Simplex II. that meets the code philosophy and requirements.Item #3: Review of 3 General methods used by Stress Analysis computer programs
Method #1:
Method #2:
Method #2 Example:
Method #3:
Method #3 Example:
Summary:
When support conditions change, superposition leads to inconsistent and less accurate results. Using AutoPIPE's method of loading sequences is much closer to reality and is used by the best known programs such as ANSYS finite element, FE -PIPE, ABAQUS, etc.
Reference:
The non-linear technical paper referenced above:
https://www.asme.org/products/books/pipe-stress-engineering
See Also
Non-linear Load Sequencing Explained