Joist Bearing on Steel Channel
Joist Bearing on Steel Channel
(OP)
I've got a situation with a enclosed second floor area that occurs in the field of a roof. The roof is occupied space with a pedestal paver system. To accommodate the finish "floor" elevations I have some conditions with hi/low framing. The change in elevation is exactly 10". In a few areas the transitions in elevation occurs away from a column so I'm providing a "stacked" beam. I've gone back and forth between making the stacked upped beam a W10x15 vs a C10x15.3. I guess my concern is the bearing length I can get with the channel. Vulcraft recommends a minimum of 2-1/2" which I will get - but barely. Has anyone else come across this or feel strongly one way or another?
I've uploaded a quick detail. The channel will be stitch welded down to the supporting beam and I'm providing a stiffener at each joist.
I've uploaded a quick detail. The channel will be stitch welded down to the supporting beam and I'm providing a stiffener at each joist.






RE: Joist Bearing on Steel Channel
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RE: Joist Bearing on Steel Channel
I agree with SRE - stack the W10s.
I would also recommend that the 2x2x1/4 angle not get welded until the slab placement is complete to avoid some unusual loading of the joist webs, as well as kicking the lower W10 towards the exterior.
Ralph
Structures Consulting
Northeast USA
RE: Joist Bearing on Steel Channel
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.
RE: Joist Bearing on Steel Channel
RHTP - I'm not quite sure I understand what you mean by "kicking the lower W10 towards the exterior". Could you clarify?
RE: Joist Bearing on Steel Channel
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.
RE: Joist Bearing on Steel Channel
RE: Joist Bearing on Steel Channel
KootK is correct.
Way back in my early years (when I detailed OW steel joists), this kind of connection, as well as bottom chord connections to columns, was a real headache for our chief engineer. When these kinds of connections are fixed before all dead loads are applied (even some live loads), the effect on the joist web members often created stress reversals. Not good if the members were not properly sized. Of course, not fixing the connection created other problems when the EoR was relying them to provide lateral stability during joist erection.
Ralph
Structures Consulting
Northeast USA
RE: Joist Bearing on Steel Channel
@Ralph: can I ask what the preferred solution is from the joist supplier perspective?
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.
RE: Joist Bearing on Steel Channel
KootK - It has been many years since I have had dealings with the manufacturers of OW joists. As things have evolved since, I may not be current. It really depends on the underlying purpose, both from the EoR's perspective AND from the steel erector's perspective.
The steel erectors look for a quick, practical and effective way to introduce as much stability in the partially erected structure. One solution was a tab welded to the column that fit between the joist bottom chord members. Obviously bolting to the tab was preferred (horizontal slot in the tab), but accuracy in joist fabrication is nowhere near the same tolerances as structural steel. Just the presence of the tab helped with side-to-side stability, but until clamped or connected, it was not the ideal simulation of a moment frame.
The EoR's were looking for a moment frame for wind (lateral) loading. Most were very understanding of need to wait until all dead loads were applied. Some tried to dream up temporary bolted 'hand-tight, weld after DL application' connections, but had minimal acceptance of the fact that OW joist tolerances were not on par with the kind of connection they dreamed up. OW steel joists are somewhat of a commodity product, produced rapidly, and not with the kind of attention to detail one can get from structural steel.
This phase of my career was well over 40 years ago so perhaps the situation has improved some.
Ralph
Structures Consulting
Northeast USA