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RE: SAC question

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Title: RE: SAC question

>In the new fema 350 there were no tests done for hollow tube moment frames.
>The recommended/pre qualified details for the w shape connection entails
>removing the back up bars ( or reinforcing it ) which cannot be done in case
>I have a hollow tube column rigidly connected to the underside of a W shape beam.

You sure couldn't remove an internal backing bar like that. And you're correct that none of the SAC/FEMA prequalification data would cover the assembly.

>Is it still possible then to have hollow tube moment connections, even
>though the back up bars are left in place, or is the conventional wisdom
>meant to disallow it? inquiring minds want to know

The intent, at least for the near term, is that project specific testing, or similar testing available in the literature, is required to justify the use of moment connections in high-seismic systems (those in the AISC Seismic Provisions). The currently available database of testing is well summarized in FEMA 350. Obviously more data (future testing) is needed to extend ranges and details.