DG9 - Torsional Braces - "Multi-span"

[Structures917]

If I have a beam that is 150' long with diaphragms at 25'-0" O.C. and a uniform torsional load acting on the beam. The diaphragms are acting as torsional supports for the beam.

would I use DG9 to check a 25' Long beam with a uniform load? or would it be a combination of a concentrated load at the start of the span, from the previous "section" plus the uniform torsion?

I ran a RISA 3d model of a 25' long beam and got similar result for the shear stress and warping stress when using the DG9; however, when I ran a model in RISA with a 150' beam, braced 25'-0" the shear stress in the beam was significantly higher. Which i'm sure its because its not just (1) 25'long beam. How would I use DG9 for this condition?

 

[structSU10]

I imagine on the 150' span the stiffness of the diaphragms and continuity (reduced stiffness compared to the 150' span) start to make a difference. As you point out the braces do not take all the torsion out of the beam so I am not sure if you can easily use the DG9 formulas to relate it. Does risa state it does torsional design per DG9? I know ram elements does say this.

 

[Boiler106]

can you really have fixity for warping stress on a 150ft long member? Seems like that would be significant and very hard to resist in order for it to develop.