struct_eeyore
Structural
- Feb 21, 2017
- 260
I have a condition where a concrete beam, running perpendicular and thru the end of a CMU wall, is experiencing an outward load (see attached section). I'm trying to reason out how much tearout capacity it has.
Here are my parameters and assumptions.
1)Shear capacity for a 8" wall w/ #5's @ 48 is 2364lb/ft - or 1575lb/8". I'm assuming this is the shear capacity of any one single shear plane within said wall.
2)There is a #5 bar running immediately thru the end of the wall, in grout filled cell, and thru the concrete beam. I'm assuming that one or two courses of the CMU immediately above and below the beam can be considered monolithic with the concrete to allow me to assume that they form simply supported beam (concrete middle, CMU block ends, with the pins being the planes of the 16" block protruding into wall). This allows me to consider 4 planes - 2 top and 2 bottom of the top and bottom 16" long block protruding into the wall.
4)The shear interlock between the blocks in the grout filled cells and between concrete is achieved via shear friction, and will be much greater than the shear capacity of the planes in the unreinforced cells.
If you're with me till this point, I now just take my four 8" long planes, x 1575lb/8" to get 6300 lb - conservative tear-out value.
What am I missing here?
Here are my parameters and assumptions.
1)Shear capacity for a 8" wall w/ #5's @ 48 is 2364lb/ft - or 1575lb/8". I'm assuming this is the shear capacity of any one single shear plane within said wall.
2)There is a #5 bar running immediately thru the end of the wall, in grout filled cell, and thru the concrete beam. I'm assuming that one or two courses of the CMU immediately above and below the beam can be considered monolithic with the concrete to allow me to assume that they form simply supported beam (concrete middle, CMU block ends, with the pins being the planes of the 16" block protruding into wall). This allows me to consider 4 planes - 2 top and 2 bottom of the top and bottom 16" long block protruding into the wall.
4)The shear interlock between the blocks in the grout filled cells and between concrete is achieved via shear friction, and will be much greater than the shear capacity of the planes in the unreinforced cells.
If you're with me till this point, I now just take my four 8" long planes, x 1575lb/8" to get 6300 lb - conservative tear-out value.
What am I missing here?
