Composite Beams with Moment Connections?? 2

[LTBGeek]

I am being asked to bid on doing the connection design for a small steel-framed addition to an existing building. In reviewing the drawings, the engineer of record has concrete slab on composite metal deck, with composite steel beams and the associated shear studs called out on the framing plans. I question this design, as the beams which are part of the moment frame MUST see some negative moment along their span, and I was under the impression that composite members could only be used in situations with positive moment only. Am I right to question his design?

 

[KootK]

It's pretty common to use composite beams in moment frames. It's much less common to count on composite behaviour in negative bending regions but even that can be done.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[LTBGeek]

Thanks - I should have just gone straight to good ol' AISC. It's got pretty good guidance on negative flexural strength for composite flexural members in chapter I. I think I had been warned off of doing this by a senior engineer long ago and had just taken it as gospel without researching.

 

[wannabeSE]

The studs on the moment frame are needed to transfer the shear from the diaphragm into the frame. In my area, the studs on moment frames are not used for composite behavior. The frame beams are designed as non-composite.