Footing Cracking Condition (ACI 318)

[EngrJS1]

Hi,

ACI 318-14 Clause No. 24.3.2 provides the maximum spacing in preventing cracks. Does this ACI provision used in designing the reinforcements of footings? If not, can somebody please explain.

 

[hokie66]

Not sure what the clause is about. Is the 'maximum spacing' to do with joints or reinforcement? If you are talking about strip footings, think about it. Would a transverse crack in a strip footing matter.

 

[le99]

Yes, if the foundation element is acting/designed as a oneway beam, or slab. The goal is to minimize the potential cracks and crack width for durability.

 

[EngrJS1]

I wasn't able to add. I am designing isolated square footings. Does the aforementioned provision still apply to this foundation type?

 

[le99]

Yes, the footing pad is dominated by one-way action. The older ACI even requires a certain amount of calculated reinforcement to be provided in the middle half to relieve the anticipated high stress in that region.

 

[HTURKAK]

My points,

- Table 24.3.2 is for Maximum (spacing of bonded reinforcement in nonprestressed and Class C prestressed one-way slabs and beams )

- When the basic formula ,( 15 * (40,000/ fs) - 2.5 Cc ) is checked for fs=40,000 psi ( for Grade 60 reinforcement ) and Cc =3 in. the max. spacing would be 15- 2.5*3= 7.5 in.

- The Clause No. 24.3.2 should be used for beams and one way slabs..