Spread Footing Min Reinf
Spread Footing Min Reinf
(OP)
I am evaluating existing spread footing built in 1973 for new horizontal vessel (boiler). Everything works but min reinforcement required for shrinkage and temperature. Per ACI318 Section 7.12. for steel Grade 40 (from 1973) it is As,min = 0.0020bh = 0.0020*20*12 = 0.48 in2. Reinforcement provided is 0.31in2 (#5 @ 12” OC). Do you know what was code requirement in 1973? Is there any “trick” to get around this requirement? If not what is the quickest fix (the client has only 20 days to replace this boiler)?






RE: Spread Footing Min Reinf
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Spread Footing Min Reinf
Moreover, if you provided 1/3 more steel than was actually required, you could use less than the minimum steel mentioned above.
Mike McCann, PE, SE (WA)
RE: Spread Footing Min Reinf
I did not know footings are female
DaveAtkins
RE: Spread Footing Min Reinf
...and usually where 'shrinkage' is involved it is a 'male thing'...Happy New Year!
RE: Spread Footing Min Reinf
"For structural slabs of uniform thickness, minimum area and maximum spacing of reinforcement in the direction of span shall be as required for shrinkage and temperature according to Section 7.12"
Section 7.12 states the following:
for Grade 40 or 50 rebar - use 0.002
For Grade 60 rebar - use 0.0018
Max. spacing = 5 times slab thickness or 18 inches.
In Chapter 15 there is no mention of minimum reinforcement for footings, only comments about distribution of rebar in rectangular footings.
So in 1977 there was no mention of footings, only slabs.
Section 10.5 in the 1983, 1989, 1992 codes all are similar.
The word "footings" shows up in 10.5.4 in the 1995 edition.
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RE: Spread Footing Min Reinf
RE: Spread Footing Min Reinf
Mike McCann, PE, SE (WA)
RE: Spread Footing Min Reinf
Mike McCann, PE, SE (WA)
RE: Spread Footing Min Reinf
iv
RE: Spread Footing Min Reinf
Answer that question the wrong way and you may get a footing inserted past your shrinkage ...