huangyhg

retaining wall temp steel
quick question. does chapter 7.12 (aci 318) apply to all flexural members for temp and shrinkage steel? it uses 'structural slab' and says it does not apply to slabs on grade, but i wasn't sure about a cantilevered retaining wall.
thanks
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applies for cant. retaining wall. not for slab on grade. imho
some designers use a better quality mix, thicker slabs and closer control joints without any wwf or rebar in slabs on grade. the commentary to 7.12.1 says "the provisions of this section are intended for structural slabs only; they are not intended for soil-supported slabs on grade"
you may want to also keep in mind the minimum flexural steel (not temp stl) at the tension face for retaining walls.
temp. steel is to primarily control cracking. generally it yield an unacceptable apperance. if the cracking acn be tolerated, then you dont need the steel. however, in terms of the overall structure, the cost of the temp steel is small.
for retaining walls, i use chapter 14.3. not 7.12.
archeng59 is right for cantilever retaining walls. we use chapter 10 for flexural design and meet 14.3.3 for horizontal temp steel. section 14.1.2 specifically states to do this.
thanks for the info. i didn't see chapter 14 until now.
i believe that the requirements of 14.3 assume a joint spacing of 20 feet. however, i can't find that provision anywhere in aci 318. perhaps the 20 foot limit is just a rule of thumb.
the portland cement association (pca) handbook, building movements and joints, discusses the 20 ft joint spacing for walls with openings and 25 ft joint spacing for walls without openings. i don't recall anything in aci 318 about joint spacing, although i recall reading (don't re
aci publishes aci 350 for environmental structures (tanks). aci 350 is very similar to aci 318, but not for temp/shrinkage steel (tanks cannot leak). aci 350 article 7.12 relates the required t/s steel to length of the wall between expansion joints: 0.3% for walls under 45 ft., 0.4% for walls to 60 ft., 0.5% over 60 ft. i use this for all my walls.

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