Elevated Concrete Slab Construction Joint Placement
Elevated Concrete Slab Construction Joint Placement
(OP)
I am designing an elevated, one-way reinforced concrete slab. The slab thickness is 9 inches. The primary reinforcment is #9 @ 11" oc top and bottom with cover of 1.5" top and bottom. The temperature steel is #5 @ 16" oc. The slab is for a 20,000 sf building. I am determining where to place the keyed construction joints. My initial thought is to place them parallel to the primary reinforcing along intermediate grid lines (no columns) in order to maintain continuity in the main reinforcing direction and splice the temperature steel. However, I can find no documentation in ACI saying this is acceptable. Instead I am directed to place the construction joints in the middle third of the slab span. Does anyone have any thoughts on the placement of the construction joints for an elevated one-way slab?






RE: Elevated Concrete Slab Construction Joint Placement
You could do it either way. Placing construction joints parallel to the slab span means having construction joints in the beams, if any.
I wouldn't use keys in slab joints. If you need shear transfer, you should use dowel bars.
RE: Elevated Concrete Slab Construction Joint Placement
RE: Elevated Concrete Slab Construction Joint Placement
RE: Elevated Concrete Slab Construction Joint Placement
RE: Elevated Concrete Slab Construction Joint Placement
With the beam cast first, there is more potential for restraint cracking of the slab perpendicular to the beam. Depending on whether this type cracking is undesirable, you may want to rethink the amount and arrangement of the crack control steel.