Corner Reinf at Exterior Supports of 2 Way Slab system with Stiff Beams

[ajk1]

In applying CSA A23.3 Clause 13.12.5 Corner Reinforcement (see attached)in 2 way slab systems with stiff beams, how should the beam inertia be calculated when determining alpha α ? Should it be based on the rectangular beam dimensions without the slab, or should it be based on the tee beam dimensions with the slab as flange?

I imagine a similar clause occurs in ACI 318 but I do not have a current copy of ACI 318. I do have my 1977 copy of ACI 318,and there they seem to say to consider the beam as a tee configuration when calculating alpha.

Also, does anyone have a worked example of the calculations for the added corner reinforcement? I can't seem to find a worked example on corner reinforcement in the the Cemenent Association of Canada Concrete Design Handbook.

 

[Lomarandil]

I can confirm that in ACI, alpha would be based on a representative tee section.

Unfortunately, it does not appear that the PCA examples include the calculation of corner reinforcement.

----
just call me Lo.

 

[ajk1]

Thank you Lo.
A supplementary question: If the corner reinforcement is placed parallel to the spans instead of diagonally, should the reinforcement per unit width be 0.707 of the amount of the reinforcement of the required diagonal reinforcement, or should it be equal to the amount of diagonal reinforcement per unit width?

Maybe I should call CAC and suggest that they include a worked example in any future edition of the Handbook.

I also notice there is a typo in the diagram on page 368 Fig N13.12.5 of the cac Hannbook: It should say clause 13.12.5.1, not 13.3.5.1.

 

[ajk1]

A follow-up question: In the Cement Association of Canada Handbook 4th edition, page 368 for "special slab reinforcement", Fig. N13.12.5, they show added reinf at all slab corners that are along the edge of the floor slab. However, the clause 13.12.5 itself, on page 126, is worded for "exterior" corners only. I interpret "exterior corners" as being only an exterior corner of the floor plate, not a corner of each panel of the floor plate. This is how we did it 50 years ago. I am curious as to what ACI does in their wording and commentary illustrations, or what other accepted publications such as CRSI or RSIC says and shows.

 

[r13]

I don't recall seeing this requirement from ACI specifications, but at practice, we usually add diagonal bars in the exterior corners as you stated. Some engineers like to add the diagonals in both ways (normal to each other), it always been a heated point of argument in the office, and create headaches for the contractors in the field. The purpose of the diagonals was to minimize effects of unaccounted forces/stresses in the corners, but according to some, it is not quite effective. I don't know if this is the same as Canadian requirement/concern.