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foundation slab + edge beam - shear forces?

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n3jc

Civil/Environmental
Nov 7, 2016
187
Greetings, let's say the structure with RC columns on the foundation slab with the edge beam around the perimeter - I'm thinking about shear forces between edge beam and foundation slab in the area of columns. There is a spike of shear forces in this area because of the large forces in columns. How much of a problem is this or am I overthinking? I haven't seen this addressed in any similar project yet. Pounching shear of the slab is not a problem since we have edge beams (bending moments + shear) but how to control the contact area between edge beam and slab around the columns?

thoughts?


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If the grade beam and slab on grade is acting together to spread the load, then you must consider the high shear force at or near the column. Looking at your foundation details, why don't you consider the option of thickening the slab under the column?
 
After obtain column reaction and soil pressure under foundation, flip your sketch and impose these loads on it, what you see - a slab on beam-column framing system, then design the components in that system.
 
1) It's absolutely correct that you could expect a shear concentration in the slab where the perimeter beam gets hung up on the slab. It's astute of you to pick up on that.

2) I feel that most engineers, if they acknowledge this issue at all, let it slide unless they are truly relying on the slab to resist the column load.

3) A perimeter beam with some depth to it will do a pretty good job of smoothing out that shear spike, as shown below.

C01_vlaehi.jpg
 
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