Q:

I am trying to compare the deflected shapes between two different models. I have the option to modify the deflected shape factor in psvdb, however I am not sure if a constant deflected shape factor would provide me comparable results. Most likely SACS is not considering the scale factor correctly.

 

R.

SACS Precede deflections were not intended to be graphically accurate as in matching the actual deflection of the structure. It is intended to show the relative magnitude of the deflections across the structure.  The scale change (V5.8 vs V23) was made in response to other engineers’ complaints that most of the time the deflected shape wasn’t visible using default values and was fixed in SACS V10.

SACS Postvue manual section 4.8 (version 23) refers the following note:

"The deflected shape of the structure is shown in relative scale not actual scale. By default, the maximum deflection is scaled or normalized for visual purposes. The deflected shape factor is applied to the default scale."

So, on a high level, you can refer the shape of the deflection but scaling the same might not be possible. You can always check the deflected curvature as SACS provides the correct one, but comparing few models with adjustment of scale is not recommended.