Crack control in flexural members

[vagarwalstr]

I am designing a retaining wall and wondering whether I should apply the crack control section 10.6.4 of ACI318? Although it says for "beams and slabs", shouldn't these be applicable to retaining walls also? Is crack control a serviceability concern or strength concern?

 

[hokie66]

Crack control is a serviceability concern. The amount of crack control reinforcement required depends on the in service environment of the building element.

 

[bpstruct]

Chapter 14 directs you back to chapter 10 for flexure in retaining walls with governing provisions of 14.3.3 for horizontal reinforcing. If you don't use huge bars in the stem, I would suspect that you aren't going to have an issue meeting this criteria. The spacing of bars required to meet flexure will probably be less than the max shown.

 

[vagarwalstr]

"Crack control is a serviceability concern. The amount of crack control reinforcement required depends on the in service environment of the building element."

Isn't serviceability more of a concern with retaining wall since crack at the back of retaining wall will allow water to penetrate through to rebar? So why don't ACI318 make it necessary to apply to retaining wall also?

 

[JedClampett]

You would think so, but in all my reading, I can't remember a concrete retaining wall failing due to corrosion. They slide or rotate, but for some reason they hold up structurally. Maybe some fail, but they don't get a journal article.
I suspect it's a combination of conservative soil loads plus conservative design.

 

[shobroco]

It's probably also because the environment is actually often good for concrete: relatively stable, high moisture content against the back surface, reducing shrinkage and cracks. Unless there are deleterious substances in the backfill, it's just the ticket.

 

[hokie66]

Vertical cracks in retaining walls are common, usually occurring at about 10' or 12' intervals. This is due to restraint by the footing. More horizontal reinforcement controls the width, but not the number, of these cracks. Ground water which leaks through these cracks will often lead to autogeneous healing. If water staining on the face is a problem, a membrane applied to the rear face is the solution.