Tying Wall Reinforcement to Slab over
Tying Wall Reinforcement to Slab over
(OP)
Hi guys,
I have a situation where I designed a precast slab to sit on top of four walls and doweled in. The contractor has come back and said they would like to use some false formwork and cast the slab in-situ. My original design only tied the walls to the slab over by dowels and therefore designed as a simply supported slab. Now, I will cog the top steel over so it laps with some welded wire fabric that I have used for crack control.
My question is, should I be concerned with the negative moment that may occur in the slab at the wall. I will assume the concrete will crack as soon as it becomes stressed and will then behave as a simply-supported slab (as per the original design). The contractor put to me that I should lap the wall steel with the bottom reinforcement but I don't think that this is required.
Can anyone see anything wrong with this approach.
I have a situation where I designed a precast slab to sit on top of four walls and doweled in. The contractor has come back and said they would like to use some false formwork and cast the slab in-situ. My original design only tied the walls to the slab over by dowels and therefore designed as a simply supported slab. Now, I will cog the top steel over so it laps with some welded wire fabric that I have used for crack control.
My question is, should I be concerned with the negative moment that may occur in the slab at the wall. I will assume the concrete will crack as soon as it becomes stressed and will then behave as a simply-supported slab (as per the original design). The contractor put to me that I should lap the wall steel with the bottom reinforcement but I don't think that this is required.
Can anyone see anything wrong with this approach.






RE: Tying Wall Reinforcement to Slab over
You really don't want to allow moment cracking right there where you have the highest shear.
RE: Tying Wall Reinforcement to Slab over
Let's say that the crack formed directly over the support centreline (point of maximum negative moment).
The joint then acts as a pin and allows rotation - so it would then act as a simple support which has already been allowed for...
If it's a highly loaded slab I would agree that the detail would be worth checking, but if the negative service moment isn't going to cause visible cracking issues I would be happy with the additional restraint provided.
RE: Tying Wall Reinforcement to Slab over
RE: Tying Wall Reinforcement to Slab over
Since you are going to re-design the slab from PC to CIP, why not make it as end fixed? If you prefer the simply supported scheme better, would bond breaker help?