Cantilever Over Head Connection

[tristan861]

I have this cantilever steel beam with overhead connection with a concrete slab - see attached sketch-. The end forces on the beam are:
M(Major) = 119 kN.M,
M(Minor) = 37 kN.M,
Shear (Major) - which will act as tension on the connection= 44 kN
Shear (Minor) = 76 kN.
My concern is how the distribution of tension on bolts would be like?, would it be OK if i treated as a base plate? or should I consider the first 2 bolts to carry the whole tension? or maybe half the bolts?
I tried to use mechanical Hilti bolts HSL-3 M24 and the ratio is OK, but I'm dealing with it as a base plate connection.

Any ideas guys? your help would be appreciated

Thanks in advance

 

[malikasal]

i would only consider the first 2 bolts to carry the tension loads!



How is the beam modeled in FE model?



ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[Ron]

All the bolts carry some tension, with the first two nearest the corner carrying the higher loads.

I would consider running an attachment plate up the concrete face to put the primary bolts in shear, not tension.

 

[KootK]

As you've identified, the issue is whether or not you'll wind up with a prying mechanism that will amplify your tension loads unpredictably. One solution could be to install a spacer plate at the front and back of the connection to create a standoff gap in between and eliminate prying potential.

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.

 

[JAE]

I think the first two bolts would probably fail very quickly in concrete break-out.

That assembly looks dangerous to me with the short embedded bolts. Might think about a way to embed a full shape in the slab and weld the cantilever to that shape.

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[dhengr]

Tristan861:
I’d make the back span length more than 650mm if I could. Then, at the location of the first two bolts, the most highly loaded by the canti. beam reaction, I would use a squared off “U” shaped anchor rod, with the two legs pointing down and threaded, for the beam top flg., and the bent portion embedded well up in the conc. wall. This should allow these two bolts to take the entire tension and distribute it to a fair length of that wall and slab.

 

[vhengr]

Is there possibility to provide additional Angle bracket?
One leg welded to top flange and other bolted/welded to side embed plate.

Cheers! -VH

 

[Agent666]

Firstly increase the lever arm, if you can to lower the load, 119kNm/0.55m = 216kN tension.... i.e. concrete unlikely to cut it in concrete breakout (depending on depth of the bolts). As someone else mentioned you want to be sure that the connection doesn't unzip, progressively pulling out the bolts.

Secondly, put first row of bolts on the center of the upstand above (unless you can move the bolts so they are in shear instead), then cast in very long bolts which lap with the reinforcement (stirrups?) in this upstand to enable you to ignore the unreinforced concrete breakout mechanism, instead lapping directly with the reinforcement. This is your best bet of transferring the load into the concrete in my opinion.

Thirdly, make sure the thin concrete section can carry the load (torsion!?)

 

[tristan861]

I appreciate all your advice. Thank you