Ribbed Slab
Ribbed Slab
(OP)
Hi,
I hear that if ribbed slab is resting on shear wall, it is a must to provide perpendicular rib parallel to shear wall,and note to let the block in touch with shear wall,since it is not safe for shear.
But I dont buy this,block is not structural element,and if rib is design for shear ,why I shall do this?
Any reference in ACI 318
I hear that if ribbed slab is resting on shear wall, it is a must to provide perpendicular rib parallel to shear wall,and note to let the block in touch with shear wall,since it is not safe for shear.
But I dont buy this,block is not structural element,and if rib is design for shear ,why I shall do this?
Any reference in ACI 318






RE: Ribbed Slab
RE: Ribbed Slab
I don't understand what the "block" represents here so I'm unable to speak to that.
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: Ribbed Slab
The concrete block is a structural element if it is a shear wall. it is possible to have a shear wall that doesn't take vertical load, but it seems like a waste of block then.
RE: Ribbed Slab
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: Ribbed Slab
So i am wondering if such statement in ACI exist,also he said the reason behind this ,is that filling block could fail under shear and separate form ribs(but I don't buy this,however there should be a reason ).
I will attach sketch after couple of hours
RE: Ribbed Slab
I know of nothing in ACI that prescribes/proscribes any of this explicitly. But then not all sound engineering practices are codified.
I think that the important part of this is the understanding that there should be competent load transfer between floor diaphragm and wall. Whether or not the infill bits touch the wall is immaterial.
In open webbed steel joist systems, we sometimes transfer shear through joist seat rollover rather than shear lugs installed between the joists. Similarly, with your rib slab may be able to transfer shear to the wall via local weak axis bending of the ribs rather than the use of a distribution rib running parallel with the wall. If you ran the numbers and it worked, I wouldn't much care if the "non-structural" infill block between ribs was in contact with the ribs/floor. I suppose this infill bits might be exposed to a very small risk of inconsequential cracking under the application of lateral load.
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: Ribbed Slab
Kootk, it does make logic now.so if the weak axis is capable to transfer load to shear wall,then no need to put crossing rib.
But my question ,how can i check this by numbers?equations?
RE: Ribbed Slab
With considerable difficulty which is why I'd probably stick with the distribution rib. I know of no established procedure to check this but we could probably make something up:
Take a 1' strip of slab parallel to the wall and treat it like a pinned based, multi bay moment frame of unreinforced concrete. You could use inflection point assumptions similar to those used in the portal frame method to simplify the problem.
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.