IMF Frame in SDC D 1

[wyeit]

I am currently designing a steel intermediate moment frame (IMF)in seismic design class D for two large garage door openings in a residential structure.

As a result of my code research, it is my understanding that any FEMA 350 prequalified moment connection can be used with the 2002 Seismic Provisions IMF. Is this correct? Can the WUF-B connection be used in this application?

For the stuctural analysis of this frame, I have assumed the column bases to be pinned. Can I assume that the pre-qualified fully restrained connections contained in FEMA 350 are rotation fixed and translation free?

Can a girder supporting floor joists be connected to the weak axis of the center column in the aforementioned frame?

Thanks for your time,

Duane

 

[14159]

I used either a WUF-B or WUF-W (can't remember which) in an IMF in SDC D a couple of years ago. I don't have the FEMA 350 now but researched it ad nauseam back then, so I think the answer is yes - you can use these prequalified joints in an IMF.

I don't understand "rotation fixed and translation free." The first part I understand -- it's about as FR as a joint can get. Translation free?

Girder connected to the weak axis of the column: I am 95% sure that this is acceptable. I know I did it on that job. I know that it is NOT ok to connect to the IMF beam in some portion, but can't remember where. This has something to do with the assumed plastic hinge location. The issue with the column is that you're likely to have doubler plates and stiffeners to detail around if you have high spectral accelerations.

I'm not sure why you want to use pinned bases. I've read this lots of times but every single frame column designed at my last firm was designed as fixed. We just design the base plate and footing for the moment.

If you're an AISC member, you should post this as a question. Go to

http://www.aisc.org

and click the "contact us" link near the top and ask your technical question. Sergio and pals usually send great answers back really fast.

I hope this helps.

DBD