Reality check for a cantilever walkway.

[Tinguindin]

I did a quick calc for a 6" cantilever concrete walkway, I would like to know if i am missing something. My minimum reinforcement looks iffy.

Thanks

Attached is the file,

 

[frv]

A few issues..

1. Your minimum depth is L/10 for cantilevered slabs (w/o checking deflections)

2. Your actual "d" is 2", not 1. (1 1/2" clear cover - 0.5"/2)

3. Why are you guessing for "a", you should be able to solve for this with strain compatibility and summation of forces.

 

[frv]

btw.. point 1 above means your slab should be at least 6.6 inches (say 6 3/4")

 

[frv]

doh!

d= 4", not 5 is what I meant to write.

 

[jike]

I am not familiar with LABC but ACI 318 requires U = 1.2D + 1.6L.

This gives a wu = 0.25 ksf and Mu = 3.78 ft-kips. I am not sure why you are guessing at "a" when you can calculate it directly....a = As x Fy / (0.85 x f'c x b)

phi Mn = 3.47 ft-kips (#4 @ 12" oc) < 3.78 ft-kips NG

use #4 @ 10' oc

Should you be using ACI 350 for a hydroplant to control cracking? This would require #4 @ 8" oc.

 

[Tinguindin]

Thank you guys,

I am a beginner and have found this forum to be great.

Thanks once again.

 

[csd72]

Tinguindin,

Keep at it, we have all been there!

 

[Tomfh]

I would anchor to the back face of the wall, make the cog longer, and put in a corner bar.

 

[hokie66]

I agree with others on flexural steel. For the shrinkage crack control steel parallel to wall, I would beef that up in a hydro plant. Outstanding projections like this crack due to differential shrinkage. The Australian code AS3600 specifies .006 Ag for a strong degree of crack control.

 

[hokie66]

You should consider the construction joints you want and show them on the drawing. Three possible ways: 1) CJ both top and bottom of slab; 2) CJ top of slab only, cast slab with lower wall; 3) Rebate in wall, no CJ extending through. I would use 180 degree hooks extending to the back face of the wall, hooked around a vertical bar. Or better yet, make the bars into "U" bars around two verticals.