Clear Cover Tilt Panels

[NewbieStruct]

I am reviewing some shop drawings for tilt up panels. Are the cover requirements different than ACI 318. For example, #6 rebar is shown with a cover of 1" rather than 2" per ACI 318.

 

[BAretired]

Who cares? Use engineering judgment.

BA

 

[OHIOMatt]

No, ACI 318 covers this. You may want to read the provisions, as cover can be reduced in certain instances (depending on panel coatings and exposure). What do the design drawings indicate? If the panel was designed with more cover, and thus a smaller "d", go with the design. Extra cover will not hurt.

 

[ztengguy]

is that on the inside or outside face? Inside face I wouldnt worry about. Outside face, might be an issue, more for seeing the rebar transmitting thru.

 

[NewbieStruct]

The rebar is at the outside and inside face both. It seems that the covers are per ACI 551. It is under the assumption that the tilt panel is manufactured close to precast plant conditions. Is that a good assumption while casting panels on the field?

 

[ron9876]

ACI allows you to treat tilt wall panels as precast concrete if I remember correctly.

 

[briancpotter]

From ACI 318:

"Structural elements precast at the job site will also qualify under this section if the control of form dimensions, placing of reinforcement, quality control of concrete, and curing procedure are equal to that normally expected in a plant"

So whether it's reasonable or not depends on the quality control procedures and tolerances used on-site.

Brian C Potter, PE

http://simplesupports.wordpress.com

 

[spats]

To make a long story short, the ACI 551.2R-10 "Design Guide for Tilt-Up Concrete Panels" recommends the following clear concrete cover:
Main Reinforcing:
Outside face of panel: 1"
Inside face of panel: 3/4"
Edge of panel: 2"
Ties & stirrups:
Inside or outside face: 3/4"
Edge of panel: 1 1/2"
It goes on to say "Some contractors have reported that concrete covers of less than 1 in. on the inside face (normally the top face of the cast panel) make it difficult to finish the panel surface. In addition, bars with shallow cover on the outside face tend to mirror through the concrete surface. Concrete cover may have to be adjusted for fire rating requirements, or where reveals, recesses, architectural form liners, or sand blasting are used on the outside face of the panel."

 

[frv]

1" is acceptable, but make sure there are no reveals.

 

[TXStructural]

And make sure you are not lap splicing bars with that thin of cover as the confinement of the splices.

 

[TXStructural]

I should add that aggregate size and exposures that demand higher durability requirements may necessitate thicker cover. Also, the ACI 318 cover requirements are nominal not minimum, and are subject to tolerances. I think those 551 covers may be minimum (are subject to tighter tolerances), as ACI 117 (Tolerances) no longer applies to precast.

 

[NewbieStruct]

Thank you guys. I will make sure that there are not any reveals and also look into the concrete mix design as TXstructural suggested.