Punching shear check - question
Punching shear check - question
(OP)
Hello everybody,
I have a question regard to the punching shear check for slabs. In EC2 (and i assume in other codes too) they say that you have to check first on "u0" perimeter (perimeter at the face of the column edge) that the punching stress is lower then a compression-like concrete strength "vRd,max" (and i said compression-like because the basic formula is used for determine the compression strength for a biaxial loading (compression on the bottom and the top face of the cube and tensile on the lateral faces); on the formula here, for punching shear, is added an 0.5 factor, dont know why). So my question is, why should we check the compression strut if we will put specific reinforcement for this ? I mean what will be happening if this doesnt check and the concrete will crack/fail? We have reinforcement anyway so.. maybe i dont understand very well how shear stress/forces are flowing/transfer though the concrete element.
Thank you !
I have a question regard to the punching shear check for slabs. In EC2 (and i assume in other codes too) they say that you have to check first on "u0" perimeter (perimeter at the face of the column edge) that the punching stress is lower then a compression-like concrete strength "vRd,max" (and i said compression-like because the basic formula is used for determine the compression strength for a biaxial loading (compression on the bottom and the top face of the cube and tensile on the lateral faces); on the formula here, for punching shear, is added an 0.5 factor, dont know why). So my question is, why should we check the compression strut if we will put specific reinforcement for this ? I mean what will be happening if this doesnt check and the concrete will crack/fail? We have reinforcement anyway so.. maybe i dont understand very well how shear stress/forces are flowing/transfer though the concrete element.
Thank you !






RE: Punching shear check - question
RE: Punching shear check - question
PS: I draw a picture :
RE: Punching shear check - question
There appears to be a fundamental misunderstanding in your thinking here. Concrete reinforcement generally does not resist load by itself. Rather, it resists load in concert with the concrete struts that restrain the ties. And those struts still have practical strength limits even when the ties are present.
The situation is analogous to that with stirrups in a simple beam. Imagine what would happen to the tie/stirrup reinforced beam shown below if the concrete struts (dashed lines) gave way. All of the rectangular panels between stirrups would rack in shear and the beam would collapse.
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: Punching shear check - question
RE: Punching shear check - question
In the sketch that I posted above, the steel ties and concrete struts work together, in concert, to form a truss that resists load. If you removed the struts from that truss, it would no longer be stable/viable.
If that doesn't help, let me know. We'll get it cleared up if takes 100 sketches.
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: Punching shear check - question
RE: Punching shear check - question
Let's give this one last try. Imagine a one dimensional version of punching shear.
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: Punching shear check - question
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: Punching shear check - question