Concrete reinforcing questionàà 3

[3doorsdwn]

If you have a massive pedestal (say 12’x12’)......do you have to provide an INERIOR row of vertical reinforcement? At what point does the size of the pedestal (i.e. x-feet by x-feet, or larger) dictate this? Is it really just a matter of trying to get the required 1% of vertical reinforcement when placing that much rebar around the perimeter isn’t feasible?

 

[csd72]

See if it works as mass concrete, then the minimum reinforcement rules dont apply.

csd

 

[J1D]

I believe the 1% vertical reinf ratio was from the column. We use this for steel column pedestal as well for a rough guide. For massive pedestal, such as the octagonal pedestal for vertical vessel, however, this ratio will be overkill. You cannot even make it to keep the minimum rebar spacing. The dowels (vertical reinf around the octagon) is calculated to resist the overturning bending moment. In addition, there is minimum amount in practice, for example, #6 to #9 rabar @6" to 10" (around the perimeter only)are what we used.

Maybe there is a ratio as minimum, but should not be 1%.

 

[3doorsdwn]

csd72, what do you mean by making it work as "mass concrete"? I'm not sure what that means. Thanks in advance.

 

[csd72]

Structural Plain concrete as per chapter22 of ACI318.

You can use this chapter even if it has reinforcement.

I would put shrinkage reo in anyway.

csd

 

[hokie66]

It would help to know what your pedestal is doing. You may be able to treat it as a wall all around, say a foot thick, with mass concrete infill. The 1% rule does not envisage a large element like this. What is the height of the pedestal and what are the loading conditions?

 

[3doorsdwn]

Thanks csd. It's been a long time since I've looked at that chapter.

hokie 66, I've got a 8' tall pedistal 12'x12' supporting a light peice of equipment.

 

[hokie66]

In that case, I would reinforce the sides as a wall and leave it at that. It is just mass concrete and can be treated as plain concrete as CSD72 advised.