Deflections on Risa 3d and SAP2000 1

[Kin1234]

Hi Guys,

I am trying to size up a two-story, two-bay steel moment frame in SAP2000. Then I noticed the deflection of the moment frame in SAP2000 is 30% less than Risa 3D analysis. I check the properties of the materials, the shear and the moment reaction forces for the members of the moment frames in both SAP2000 and Risa 3D analysis, they are the same. I am having hard time to figure out why the deflection is different between the SAP2000 and Risa 3D analysis and wondering if anyone know why?

Thanks,

 

[jayrod12]

If you're using the US codes, I believe Risa applies a stiffness reduction factor.

 

[JAE]

Agree with jayrod12. This is a checkbox on each member's properties.

 

[JLNJ]

It's part of the stiffness reduction for P-delta. You can toggle it off if you want the full stiffnesses of the members.

 

[Kin1234]

Got it. Thanks for the help.