Assessment of Joist Girder Connection to Concrete Column

[generick]

Hello all,

How would you all approach this problem in terms of assessing whether this connection can support factored girder load of a 145 kips? See sketch and my understanding of the load path. If there is also a textbook reference or similar calculation done, that would be even more helpful. My initial attempt was to:

1) Check angle in shear (assuming no stiffener)
2) Check weld strength
3) Check studs
4) Check weld strength of bolts to embed plate

Thanks and appreciate any insight, I mainly practice with concrete and have been trying to familiarize myself with steel design through online resources.

 

[Brad805]

145kip each? If so, I would stop looking at this connection detail. It does not work.

Column dimensions?

 

[driftLimiter]

The SEOAC Structural Design Manual Volume 2 has a really good example of how to design these embeds for vertical and axial load. But I prefer columns

 

[GC_Hopi]

The eccentricity from the girder causes a moment which in turn create moment on your embed plate. This moment would be resisted by tension and compression. This should be added to your FBD.

 

[le99]

I would place the joists beside the column. The floor load shall be transferred to the beams, then from beams to the column.

 

[EZBuilding]

I'd start looking at a concrete corbel on each side. Would be nice to have your tension forces from the eccentricity counteracting against each other through the whole depth of the column. Right now you have those shallow studs with large tension loads adjacent to each other. I'm not sure how one would incorporate that into an anchorage design. Possibly making the depth of the concrete element half of the column width?

 

[generick]

@Brad805
The columns are 24"x24". To break it down further, the unfactored DL is 38 k and floor LL is 63 k. Can you express why the detail won't work for this loading? I was looking at concrete corbel but wanted to assess if this connection could handle it.

@driftLimiter
Thanks! I'll check that out.

@GC Hopi
Thanks for catching that, I have updated my FBD.

@le99
The OWSJ frames into the girder in which the girder dumps the load into the column already.

@EZBuilding
I agree, before I started to get into assessing it the first thing that popped into my head was those headed studs. I can't imagine these having an easy placement in line with the column's reinforcing.

 

[le99]

Ideally, you should place/bear all joists on the girders, not the column.

 

[generick]

@le99

I attached a snippet of the ETABS model that I have with the joist bearing on the girder while the girder bears on the columns. I believe I may have confused you into thinking that the joist goes directly to the columns.

 

[Brad805]

We had a discussion not long ago with a long time member. His reaction was something like 100kip on one side. I will try to find it again. For the life of me I cannot recall who it was or the title. In that discussion one member posted a link to the design for heavily loaded embeds, but that does not follow the common design methods used for headed concrete anchors.

Your loads are too large for simple methods typically used for the design of headed concrete anchors given your column width. I pasted a 5min trial with a embed if this were one sided.

To get an idea of the capacities I would look at some of the connections on the market to replace corbels. Meadow Burke, Piekko, Halfen and other have some good products. The Halfen HUC anchors might be a good option, but they do take a while to procure.
Meadow Burke

 

[generick]

@Brad805

Thanks for the clarification as well as adding the connection results for one side of the column. I am convinced to just proceed with designing a concrete corbel now. Also, unfamiliar with the program output but does T-V signify Tension-Shear?