cmu corbel / ledge design

[JimValentine]

Anyone know where to find info on designing a cmu ledge for supporting second floor wood i-joists? (2 story building)
I'm planning on using an 8" cmu wall, and then corbel-out two courses of 12" cmu to create a bearing ledge for the joists.
Not sure how to reinforce the 12" courses.
Thanks.

 

[tony1851]

Why a corbel? Can you not use joist hangers?

 

[JimValentine]

Originally the floor LL was 60 psf, but now the owner wants to use 100 psf. My original detail was to use an 8x4 ledger angle with bolts every 24", but the bump in live load required too many bolts. So I decided to find another option. Maybe I'll look at using hangers screwed directly to the block with Simpson Titens. Thanks Tony.

 

[a2mfk]

You could use a concrete tie beam unless it is exposed CMU, and you can get much higher bolt values or use a CIP connection.

 

[JimValentine]

A concrete beam was definitely one of the other options, but I decided that getting the two trades involved wouldn't be efficient.

 

[kipfoot]

There's a mention in ACI 530-13, section 5.5, which refers you later chapters:

5.5.1 Load-bearing corbels
Load bearing corbels shall be designed in accordance with Chapter 8, 9, or 10.

So, your on your own with engineering principles and basic masonry design for shear and bending due to eccentricity in the wall.

I'll add that 11.1.10 states that "Load-bearing corbels of AAC masonry shall no be permitted." (autoclaved aerated concrete)

 

[XR250]

Why not add an angle iron below your ledger - bolted to the 8" CMU?