Punching Shear in Transfer Beams

[efFeb]

Good Morning,
I've been thinking about punching shear requirements for wide, shallow beams like slab bands, and am wondering if anyone has any good resources or thoughts on how and when to consider / check punching shear in transfer beams?
Thanks,

 

[jayrod12]

Check it all the time, it really is not like it's a difficult check to make.

 

[rapt]

If a punching perimeter can form within the band beam width (length of the punching perimeter around the column less than the 2 * Bw), I would check it.

 

[r13]

If the beam is capable of support two way action, and demonstrate two way behavior, yes, check it.

 

[Tomfh]

If a punching failure is potentially more critical than one way shear, i.e. if the punching perimeter can form inside the band, then check punching shear.

 

[rowingengineer]

Why the band beam? Are you thinking in a similar for torsion the the slab on each side of the beam will act as a solid plate causing tension stiffening that allows for better shear/torsion results to also apply would also be applicable to punching shear.

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

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[r13]

Punching shear is a phenomenon in flat slabs caused by concentrated support reactions inducing a cone shaped perforation starting from the top surface of the slab. Although generally preceded by flexural failure, punching shear is a brittle failure mode and the risk of progressive collapse requires a higher safety class in structural design.

One way shear is rate of change of bending moment. It's typically called beam shear. However two way shear is punching shear and its effect is two way. It's also called flat slab shear.

 

[efFeb]

Thanks for your responses; I've attached a sketch to show a particular condition i'm worried about.
The location of the column transfer means that there is definitely enough room for the punching perimeter to form. This leaves me with a few questions, sorry if some of these are obvious answers:
1. I'm also going to need hanger stirrups at the beam intersection; is this in addition to any required punching shear reinforcing? Does anyone have detailing suggestions for this?
2. I have a thin slab outside of the transfer beams, but is there any reason I would need to treat this as an edge condition?
3. If I do need stirrups for punching shear reinforcing, i cant extend this 2d from the face on all sides, as I run off the beam. Does this mean I must widen the beam, or as i mentioned above, does this create an edge condition.

Thanks very much for your help!

 

[r13]

I hope the sketch below can help you to realize the difference between one way and two way actions from deflection point of view.

I don't quite follow your question. Can you provide a cross section on each beam, and show where is the slab of your concern?

 

[Celt83]

I take the same approach Rapt noted if a full punch perimeter can form within the width of the beam the look at a true punching check. If the punch perimeter would fall outside of the beam then fall back to traditional one-way beam shear and beam stirrup design.

I usually take a conservative approach and the hanger bars should be designed to transfer the full column reaction + any tributary floor load into the supporting girder.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer