I have a model with x bracing and my angle sections are experiencing compression for repeat load cases which has dead and a lateral load combined? All other cases are showing tension only except for these cases? Also I have compression in those members along the full length (not like others have issues where its tension in one end and compression in other). Why is it happening?
I have uploaded the file via secure upload.
The results for load combinations 102, 103 and 104 are not as expected, because these combinations are not converging in the iterative tension only analysis. Warnings are reported in the Output file mentioning this. As long as the analysis does not converge, we cannot trust the results. The analysis in non-converging, because the structure becomes unstable when the lateral forces are applied. I am not sure yet how to make it stable though.
What can I do to fix it now?
To get rid of instabilities, you can provide a small rotation spring about MZ DOF instead of full MZ release for supports 71 TO 77.
Also, add SET ITERLIM 20 command before the JOINT COORDINATES line in the input file.