Slab - wall connection

[oranda]

When pouring concrete slab against another concrete/precast wall, what is the main purpose of having starter bars protruding from the wall into the slab. Genernally, there will be sufficient rebate (ie. 25mm - 30mm) in the wall to support the slab already.

 

[whymrg]

You need to connect wall to diaphragm (slab) to transfer shear due to wind and seismic loads (on structure) from slab to wall and then to footing. Also you need to support wall for out of plain wind and seismic load on wall itself.

This is required by Building Code.

 

[ishvaaag]

Also a 25 or 30 mm support is very doubtful to stand full lenghth without disengagement a mid force earthquake; the same can be said about a fortuit explosion and at any progressive collapse situation. So ensuring some connection is important to prevent the loss of geometry, the fall of the slab, and human loss.

 

[dlew]

oranda,

Those bars are not to transmit the shear from the slab to the wall. The shear is transmitted by a shear key or a rough surface. The rebars are used to keep the two elements acting together, for shear friction if only a rough surface is used, and to transmit other horizontal forces and moments from the slab to the wall.

AEF