Temperature Reinforcement - Strip Footings 5

[chevyman56]

ACI 318 does not seem to address minimum temp reinforcement in continuous wall footings. I have been just using "rule of thumb" type reinforcement minimums for 9 years since college. Does anyone know where I can get info on the IBC code required temperature reinforcement for continuous/strip wall footings?? The inspectors do not even know!! They just know that the footings should have some.

 

[miecz]

None is required. So what if the footing cracks?

 

[JAE]

ACI 318 - section 10.5.4 seems to imply that footings should use the min. temp steel of section 7.12, which is for slabs.

 

[WillisV]

For the transverse direction, the wall strip footing can normally easily handle the loads required when designed as a "plain concrete" section per ACI - no steel required. I typically put in 0.0018bd in the continuous direction just to give the wall dowels something to sit on.

 

[miecz]

ACI 318 Chapter 22 allows strip footings to be plain concrete. The commentary to article 22.3 specifically addresses continuous wall footings.

 

[archeng59]

I always put at least 2 #5 continuous in the bottom of a strip footing. If the footing depth is 18" or greater, I use top and bottom bars with stirrups spaced at 16" o.c. in my opinion, plain concrete does not mean "unreinforced". but there are no requirements for minimum reinforcing in plain concrete.

for a strip footing supporting a load bearing wall, if calculations show that no reinforcing is required for shear or flexure, I use ACI 318, 14.3 as a guide for minimum reinforcing.

based on my own experience, most building officials expect to see reinforcing in concrete and many city/county/state codes required at least 2 #5 bars in a footing, or #5 spaced at 12" o.c. each way. Contractors typically call a strip footing a "grade beam" and they are used to seeing reinforcing in a grade beam. providing some type of reinforcing will certainly eliminate the arguments with a contractor or city/county/state inspector.

 

[aggman]

If the wall is designed as reinforced then ACI 318-02 states in section 10.5.4 that footings should have the minimum as is required per section 7.12. This would require .0018 * b * h for Grade 60 reinforcement. (h is the depth of the section, not the effective depth.)

 

[archeng59]

thanks, aggman. I remember that now. that provision was revised in the ACI 318-95 to include "footings". I started using chapter 14 minimums for horizontal steel (0.002xbxh) in footings before the code changed to what is now shown in 10.5.4. because I didn't have anything more specific to use. old habits die hard.

 

[miecz]

ACI 10.5 applies only to flexural members. Article 10.5.4 specifies minimum reinforcing "in the direction of the span". If your strip footing is a flexural member, then you need to meet 10.5.4. Otherwise, Article 22.3 applies.

 

[archeng59]

in my opinion, chapter 14 is applicable for the steel parallel to the length of the wall. 10.5.4 could be used for temp steel since there is no specific requirement for "temp" steel in a footing. in ACI 318-02, article 22.3 makes no reference to reinforcing requirements.