Where are you seeing this clause of concrete breakout doesn’t apply to embedments deeper than 20d? Based on below snapshot, full bar development does not preclude breakout on cast-in reinforcement.
I think the way you broke up the load path makes sense and should be conservative.
If you need more capacity, I would think you can use a wider beam A. Perhaps flare out at 45 from the center of column.
There is no biaxial bending at point A - you have normal stresses in orthogonal...
You beam is narrow, you will not be able to increase your breakout capacity with additional anchors.
If you have top rebar available, you can justify this with anchor reinforcing:
Refer to ACI chapter 17.
For examples, refer to "Companion to ACI 318-14" and "PIP STE05121".
You might be able to compare to some FM Global Roof Nav assemblies. Not sure what your wind load is but say it’s 45 PSF ULS unfactored, you can copy the fastening of an FM 1-90 roof assembly (failure load of 90 psf).
Josh, I've seen some of your posts before regarding your work for software companies...
What kind of a role did you have starting out and what do you do now if you don't mind me asking.
Did you start out coding? Did you have experience coding beforehand?
I find myself very interested in...
If you are not very familiar with “anchor reinforcing” (which is basically “lapping), good starting points are AISC Design Guide 1, Companion to ACI 318, PIP STE0 5121, ACI 318-19, and of course the Hilti technical guide. Most of these articles are for “lapping” cast in anchors but I am hopeful...
you might be able to “lap” the anchor with the vertical wall reinforcing to preclude breakout.
Hilti has a technical guide with examples for this situation. They also have a free software for this.
I agree with your assessment of this method. Certainly a few loose strings. Admittedly, I have used this method and certainly haven't done any bending checks on the "spreader" bars, nor considered any eccentricity on the tie.
I think I understand your point of the leading bar bending/curving at...
In the strut and tie model I posted above (I think you call this the Widianto method), we pass the shear to the dowels and preclude breakout from the ties anchoring them.
Your comments on shear friction: the friction from the normal force on the strut, the drag tie, the partial development of...
In method 2b, I am picturing the diagonal concrete strut bearing directly on the vertical pier bars at the leading edge (at the cold joint). The shear is transferred through the leading bar in direct shear. The leading rebar is then designed for breakout/pryout/etc. from the slab as a dowel...
I don't see bars breaking out from the pier as an issue (at the slab/pier joint).
The way I see it, breakout is precluded from the diagonal concrete strut to the top tie.
Looking at this problem with some fresh eyes, I think you can break up the steps like this:
Top of pier mechanisms:
1.a...
Thanks for the reply Kootk.
OK, let's say the low tie doesn't adequately transfer the shear to the rear bars, can you still design the front bars as dowels?
So the front bars would be designed for breakout from the slab and the rear bars designed for the tension breakout (or bond failure) from...
I've got a small column pier (9" high) sitting on an 8" elevated slab (dowels post-installed into slab).
Curious how others justify shear transfer at the slab/pier joint?
In a normal pier/footing case, I would develop the bars above/below the pier/footing joint and use the shear friction...
Providing tower bracing is preferred but you certainly can do it.
If the stringer is attached to a slab, you’ll only have a one bolt connection likely.
Also you should play close attention to the flexibility of the stringer/tower connection.
Another option is to provide a knee brace from...
I've never done this design before but you can Hilti those in by the development length and rely on shear friction for the shear at the joint.
You might want to consider the cold joint at the sidewalk.
Hilti has a guide with examples for slab extensions.
If you can get one stirrup near the top of pedestal (within the 5"), you can do a strut and tie check for the high shear load. Refer to PIP STEO5121.
Alternately, you can check your concrete breakout strength and other anchorage requirements from your code.
Agree with Dave.
If you need to squeeze more capacity out of an existing beam, you can add bottom flange braces or increase your Cb factor.
See AISC commentary, section F1.
There is a formula that allows you to make use of top flange support for negative bending.
