The diaphragm design in the manual is based upon the shear friction
approach. Wire mesh in the slab provides for crack control and strength.
This is no different than any other reinforced concrete member in that the
reinforcement is only really required when it cracks. At the perimeter of
the slab I usually have some rebar because of cantilevered slab details or
in this case brick veneer angle supports. I usually thicken the slab at the
edge as well.
At 12:30 PM 1/25/00 EST, you wrote:
>I have always designed for LL + Brick Load with deflection criteria of
>L/700. A lot of times the Dead Load will all ready be on the beam so that
>deflection doesn't come into play.
>You say you are using the Hambro joist system. That system scares me as if I
>recall the slab has no decking and the concrete is only about 3" thick. What
>happens if the slab cracks. You lose your diaphragm capabilities. Hambro
>will not guarantee that the slab will not crack.
David Handy, P.Eng.
The Thompson Rosemount Group, Cornwall, Ont. Canada
Opinions expressed are personal only.