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ACI 318 ch 7 question
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FFENGINEER
Structural
wouldnt the maximum be what you need for design? Min cover for concrete against earth should be 3 inches
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well, the design was 3/4" from the top of the stem wall and 3" from the sides. If the rebar was placed more than 3/4" from the top of the wall they are out of spec. Everything is minimum per aci...I am trying to understand what would maximum be, if there is is one per code. The engineer did not specify on the drawings or specs. I am trying to understand the table and wording in ch 7.5.2.1 for clarification.
FFENGINEER
Structural
When you say from the top, you mean down from the top? I would say you are ok, If the bars are in teh top, they are really compression bars if anything. Perhaps a sketch would help
theonlynamenottaken
Structural
Ok, you're really asking two separate questions here because of the way you worded it.
1) Is there such a thing as maximum COVER?
"Cover" is there to protect steel reinforcing from the environment outside of the concrete member. Based on that definition there is no such thing as maximum cover. However, eventually you would have to consider drying and temperature shrinkage effects on the unreinforced mass of concrete that falls outside of the reinforcing.
2) How far from the surface would the reinforcing have to be to become structurally inefficient/inadequate?
The design engineer should specify where within the member the reinforcing should be, in addition to the minimum cover appropriate for the anticipated conditions. Sometimes a tolerance of placement is warranted. Where the reinforcing falls within a member essentially dictates its structural behavior, capacity and functionality (i.e. If you put reinforcing only on the compression side of a flexural member you really only have plain concrete behavior, not reinforced concrete)
It sounds suspiciously like the design engineer specified the bar size and the minimum cover, but did not state the placement. Some engineers find that drawing the bar close to one side or the other of a member is enough of a placement specification, though I disagree. At very least the placement should be state textually in a note (i.e. @ mid-depth of slab, 3" from top face of beam, etc)
1) Is there such a thing as maximum COVER?
"Cover" is there to protect steel reinforcing from the environment outside of the concrete member. Based on that definition there is no such thing as maximum cover. However, eventually you would have to consider drying and temperature shrinkage effects on the unreinforced mass of concrete that falls outside of the reinforcing.
2) How far from the surface would the reinforcing have to be to become structurally inefficient/inadequate?
The design engineer should specify where within the member the reinforcing should be, in addition to the minimum cover appropriate for the anticipated conditions. Sometimes a tolerance of placement is warranted. Where the reinforcing falls within a member essentially dictates its structural behavior, capacity and functionality (i.e. If you put reinforcing only on the compression side of a flexural member you really only have plain concrete behavior, not reinforced concrete)
It sounds suspiciously like the design engineer specified the bar size and the minimum cover, but did not state the placement. Some engineers find that drawing the bar close to one side or the other of a member is enough of a placement specification, though I disagree. At very least the placement should be state textually in a note (i.e. @ mid-depth of slab, 3" from top face of beam, etc)
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