Learning Forum

[matt]

Folks, the results from response spectrum lose their sign during the MCOM arithmetic.  What if I added syntax to the MCOM file to store the sign for the node and element results prior to the arithmetic in MCOM and then reapplied the signs afterward?  Do you think that’s plausible, or does that upend the basic theory of the combination somehow?

[dlooman]

I don't see how that could work.  The sign of the node and element results could be plus or minus depending on the mode.  You could create your own combination method in which you algebraically sum the model results without doing any squaring.

[danielshaw]

What is your goal?

For a response spectrum analysis, the contribution from the individual modes must be summed.  The direction is not known, so some form of SRSS is used.  What signs are you saving and how will you reapply them?