transfer slab - beam shear and punching shear reinforcement

[asixth]

Hi

I have a transfer slab/beam where the shear stresses are high. With propriety stud rail reinforcement, I understand this to be fully developed vertical reinforcement which increases the shear capacity. My question is whether anchored shear ligs / links would perform the same task.

Also, are there any methods out there that I can use to increase the shear capacity of a concrete slab band. The idea's I have are to stress the slab and to use a high grade steel for shear reinforcement. What is the highest grade steel that is available on the market. Is there any grades higher than 500MPa or 75ksi?

Thanks.

 

[bookowski]

Yes, you can also use traditional shear reinforcement instead of studrails. You can also use bent up bars. The problem with using traditional shear reinforcement is bending legs that small and assuring the proper layout, but if you have a very thick slab this may not be a problem at all. Studrails are easy and you know that the layout is exact. If you do a search on the web for ACI 421 and punching shear you will find some papers on the topic. They generally state that studrails work better than hooked rebar legs but you can still do it.

For your 2nd question - there is very high grade steel but ACI sets limits on what you can use to insure deformations compatibility. If you are outside the US then check your local code, there are probably similar limits.

 

[ron9876]

Sounds like you have a point load close to a support. You can use a bottom drop plus reinforcement/stud rails to increase capacity.

 

[hokie66]

I wouldn't want to use a higher grade steel than 500 MPa. Besides being not available, high strength steel doesn't have the bending ductility required for fitments.

I'm not a fan of studrails. Have you considered a structural steel shear head?

 

[rowingengineer]

I have attached a document that discusses different shear reinforcing methods. Not a great fan of shear studs, would prefer increased depth of a drop panel myself, but I assume this isn't an option.

http://www.nceng.com.au/

"A safe structure will be the one whose weakest link is never overloaded by the greatest force to which the structure is subjected” Petroski 1992

 

[asixth]

Thanks guys. I think I just undersized the transfer slab. My shear forces are howling.

@RE/hokie, good to see you guys are still going strong. I kinda got lost in the woods there for the last year.

 

[hokie66]

We have missed you. Yes, you don't want to skimp on depth in transfer slabs. The issue is usually punching shear, and the solutions involve either more depth or larger columns. I tend to use punching shear as the controlling criteria for depth selection. The ACI code does allow a bit of assistance from prestress, but not sure if this has been as yet adopted in the Australian standards.

 

[rowingengineer]

good to have you back on board, good to see you have figured this one out, why you are doing this on a Sunday well that is another issue.

http://www.nceng.com.au/

"A safe structure will be the one whose weakest link is never overloaded by the greatest force to which the structure is subjected” Petroski 1992