In Wall flush beam ICF

[southard2]

I am designing a 6 1/4 inch wide ICF wall beam with an 18 foot span. I have 9 feet of wall between the top of wall and top of opening. Since its an ICF wall I want to avoid shear stirrups if possible. I'd like to place (2) #5 bars above the opening along with typical horizontal wall and vertical wall reinforcment with ZERO shear stirrups. What depth (d) can I use in my phiVc calculations. I think I can use the whole 9 feet if I needed to, however in the past (I do lots of tilt-up) I have always been conservative and placed a 2 foot deep reinforced beam with shear stirrups over my openings. If the two foot deep assumption was OK without shear stirrups I excluded them. If it wasn't then I would include them.

In either case this beam won't require lateral bracing. I can't be the firt person to contemplate this? I guess I'm having a bit of self doubt. Am I missing anything here?

John Southard, M.S., P.E.

http://www.pdhlibrary.com

 

[JAE]

The opening would have an arching action if you have adequate wall on either side of the opening. If you had less wall on either side, then that would create a need for tension reinforcing at the bottom of the arch (top of the opening) to tie the arch together - developed past the opening width.

With 9 feet of wall, you could also look at it as a deep beam (see ACI 318, sections 10.7 and 11.7).