APPENDIX D-Anchoring Need help with An (Projected area for groups)

[SilverBeam75]

I have two (2) anchors with a distance of 8'' between them and it is installed on a 12 in wide strip concrete wall. The anchor embeddement is 12'' deep. I've used a software for anchor analysis and it indicate a PROJECTED AREA FOR GROUPS OF ANCHOR "An" 77.5 in^2. I'm unable to verify it. What is the calculation? See attachment for more info

Thank you,

 

[dylansdad]

SB75,

I don't know where the 77.5 in^2 comes from either. I ran it through Simpson Strong-Tie Anchor designer for ACI 318 and get 501 in^2.

Assuming there are only 2 "faces" of influence it is calculated as hef=hd (12") - bolt dia. (3/4")= 11.25 in.

Distance left of bolt is 1.5*hef=16.875"
Distance between bolts is 8".
Distance right of bolt is 1.5*hef=16.875"
Width of wall is 12".

Total length is 16.875"x2+8"=41.75"
An = 41.75"x12"=501 in^2.

 

[SilverBeam75]

Hi,

Maybe a narrow modification factor must be applied ?