ACI 318 Appendix D D.6.2.1 (Avco)

[dmitriy555]

Per D.6.2.1(b) shear force perpendicular to the edge on group of anchors is Vcbg = Avc/Avco*(********)Vb

where Avco is the projected area for a single anchor in a deep member with a distance from edges equal or greater that 1.5Ca1 in the direction perpendicular to the shear fore.

Avco=4.5(Ca1)^2 (D-23)

In my example, I have a 17" square column with four (4) anchor bolts, each bolt is 6" from each side and 5" apart. So, the Ca1 = 6", thus I can not use formula (D-23). Should I calculate Avco based on my actual parameters or still use formula (D-23).

 

[anchorengineer]

Hi Dimitry,
You will still use D-23. This is just the formula to calculate the projected area for concrete breakout of a single anchor in shear. When you divide the actual breakout area (Avc) by the breakout area of a single anchor (Avco) it takes into account all of the adjustments for edge distances and depth restrictions. What your finding is how many idealized anchors you actually have. If you are designing for only one anchor, and you have no edge restrictions, the ratio of Avc/Avco = 1.If you have 2 anchors spaced at 3*Ca1 with no bottom or edge restrictions your ratio would = 2. If you are desiging 1 anchor and you have an edge or depth restriction Avc/Avco will be less than 1.

Try playing around with Hilti's Profis Program. I know Powers Fasteners just updated their PDA program but I'm not as familiar with theirs yet. Good Luck.

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