contract joint 1

[DCKlyce]

For contraction joints in a reinforced concrete wingwall that is on a spread footing, is the joint typically placed in the footing as well? The project is in Delaware. The footing has 2 feet of cover.

 

[jike]

Footings do not need contraction joints. Contraction or control joints are mainly for appearance, so we force the crack to happen at that weaken location in the wall. If a transverse crack happens in a footing, no one sees it since it is covered up with soil.

 

[hokie66]

The reason you get a crack in the wall is that the footing has restrained it. So joint only the wall. Depending on the spacing of crack control joints, you could still get cracking of the wall stem due to aforementioned restraint.

 

[DCKlyce]

On the same project, there is a box culvert (12' x 15' wide) that will serve as a pedestrian tunnel. Less than half of the tunnel would be above grade initially and in the future it would be completely buried. The tunnel is 270' long. Would a contraction joint be in the bottom of the bottom slab? Is reinforcment interupted at the contraction joint? Looking at a MD standard, it appears they use a V notch and interupt the rebar (since the notch is 3" deep)

 

[jike]

I would put a joint on all 4 sides (roof, walls and base) in a box culvert. All surfaces are exposed to view. The base is a combination footing and slab. Usually slabs have contraction joints. The depth that the structure is buried should have no influence on the need for joints.

Usually every other bar runs thru contraction joints.