What R value for moment frame with pinned base?

[MidwestSE]

Hi everybody,

We are having an internal debate - what R value is appropriate for a 1-story pinned-base moment frame with several bays? (no seismic detailing - see attached image).

Side 1: Moment frame provisions apply, R = 3.

Side 2: Column is in single curvature and moment frame provisions do not apply. Behavior is more like a cantilevered column system w/ R = 1.25 or an inverted pendulum type structure w/ R = 2.

Thanks for all your input!

 

[phamENG]

If you're not providing any seismic detailing (not detailing per AISC 341), then you'd fall into Steel Systems not Specifically Detailed to Resist Seismic Loading - R=3.

 

[strucbells]

I'd go with R = 3. The major difference from an inverted pendulum or cantilevered column system is that rotation will be fixed at the top for the pinned base moment frame.

 

[JoshPlumSE]

R = 3. There's a lot more redundancy than you'd get with an inverted pendulum or cantilevered column.