Wall dowel development - Std hook?? 3

[HeavyCivil]

For 90 degree wall dowels (from ftg's or mats) I have have typically considered that the 'A' dimension, or that which goes into the mat or footing lapping transverse bars, should be Ld, or 1.3 Ld.

It has never occured to me, until now, that the 90 degree dowel could be considered a standard hook, and that only the value L (think table A7 in CRSI's Development book) could be taken as the depth of the footing or mat, minus 3" for cover over subbase.

This is significantly less. The example I am looking at is an epoxy-coated #8 bar. The development length is 50" (class B) whereas the standard hook length is only 21". Meaning here that a 24" deep footing would be sufficient with a #8 standard hook.

Is this correct? It seams there is an opportunity to save lots of steel, assuming that the concrete depth is sufficient.

 

[ToadJones]

If I am following you correctly, I use standard hook development for pier dowells....I think ACI 12.5.2

 

[JAE]

Yes - use the hook development - not the lap length horizontally. Lap splices engage bars in the direction of the lap spliced portion of bar, which in a spread footing, is perpendicular to your vertical bar.

A standard hook for a #8 bar involves a 1'-4" leg. The hook development length l_dh would be the vertical measurement from the top of the footing down to the bottom of the horizontal hooked leg.

For your 24" thick footing you would then have 21 inches to work with.

A #8 hook development length, for f'c = 3000 psi & epoxy coated rebar is 18" per ACI 318-05.

 

[HeavyCivil]

Great - thanks for the clarification.

 

[ToadJones]

Agree with JAE 100%