Hollow core-Side cantilever-Plain concrete-ACI code

[damiller]

Does anyone know the design approach for precast prestressed hollow core plank when dealing with side cantilevers.
1)Since the plank is not reinforced in the direction perpendicular to the span, is the plank considered plain structural concrete for side cantilevers? If so, then according to ACI 318-02 22.2 it requires continuous support? But then look at the commentary R22.2.2. It contains a sentance stating "The tensile strength of concrete can be recognized in the design of members." Is this interpreted as ok only if limitations of 22.2 are satisfied?

2) ACI 318-02 22.5.1 of Strength design:
Does this only apply if limitations of 22.2 are satisfied?

3) Finally, what is the section modulus of the hollow core right at a hollow? Is it just the top and bottom flange. Then the webs, which are set back in the side view, constitute the web. Is that right?

Any comments would be appreciated.

 

[jike]

There are many things that can be done some of which would depend upon what the manufacturing process of the plank is (ie wet cast or extruded).

I assume that you have a perimeter support member set back from the cantilevered edge.

A couple of ideas:

Use conventional reinforcing in bonded topping as top steel for the cantlever. The plank designer may have to grout the cores to carry the shear.

Turn the span, if possible.

I really would suggest that you call a precaster in the area of the project and do some brainstorming.