Effective Length Method

Question

I am analyzing this braced frame structure with the effective length method following this procedure https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/55456/asce-7-aisc-360-and-the-effective-length-method-in-the-ram-structural-system 
 The drift report seems to indicate that my structure is extremely torsionally irregular. The stability coefficients report also shows that it exceeds the max allowable. 
 Before I begin adding new braced frames to my structure, is there a way to determine that the issues shown in the reports are accurate and not related to mistakes in modeling the structure?

Seth Guthrie · Answer

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 When evaluating drift it's good to check the overall deflected shape first. Your semi-rigid diaphragm might be deflecting a lot causing unexpected ratios, for example. If the deflections are reasonable, but something is off in the torsional check it could be due to having control points that are off the diaphragm. You can always calculate these ratios manually using the drift or nodal displacement results.

Seth Guthrie · Answer

There are some huge displacements of the semi-rigid diaphragm in this file, especially for the A/B roof 2 level. As such, the reporting of drift could yield some very large values depending where exactly you check for drift (in a semi-rigid diaphragm the program looks at the average displacements of the nodes of the element nearest to the control point). For this I would stick with nodal displacements because you have frames at the edges where you care most about deflections and because the diaphragms are all partial. You might also want to include the diaphragm out-of-plane stiffness under criteria - diaphragms. See: communities.bentley.com/.../ram-frame---semirigid-diaphragms-faq