Sloped Reinforced Concrete Slab

[RareBugTX]

Hi all:

We are designing a two story home where the sloped roof (10:12) is going to be reinforced concrete slab (one way for analysis).

I would like to hear if someone has dealt with this situation before, I am thinking in considering the ridge as a rigid support as it is going to be nearly perpendicular to the slab on the other side (gable roof).

Also there is going to be outward thrust at the CMU wall support on the other side. I am thinking that the beam would be subject to the lateral force as well as the gravity component.

Your thoughts are welcome.

 

[JAE]

You simply have to resolve the loads/reactions and follow the load paths through the structure. I believe it is just basic statics.

With a high pitch, yes the component in line with the intersecting roof plane can be taken by the opposing roof diaphragm, but the other orthogonal component must be dealt with as well.

 

[DST148]

Assuming no ridge beam, you could design it as a two-hinged frame. There will be thrust on the two supporting walls / beams. You could also design it as a three-hinged frame(some thing similar to three-hinged arch). There will be thrust on the supporting walls/beams.
If you provide a ridge beam which can span from gable to gable wall or other support , then slabs could be designed as spanning from side walls to ridge beam. In this case there will be no thrust on the side walls.

 

[BAretired]

Sounds like a folded plate. Give us a sketch.

BA

 

[mfrad]

In pouring the 10 on 12 slab you need to consider using a top form to avoid segregation of aggregate.

 

[ishvaaag]

Yes I had to do that on some set of houses (but reinforced concrete structure). Simply ensure that the model is correct (has all elements in place) and then the structural analysis program will identify the particular requirements for the members. Normally you may get a situation where the push of the roof interacts in with the attic floor (that seats the roof and attic loads) and just modifies the reinforcing requirements. If no attic floor, ties plus supports delivering the required rotation at the supports may be needed, except you want the outfit behave as a kinked beam spanning the whole building, and even then need for supports able to deal in rotation and lateral movement with the arch opening under the weight and loads, and so a reasonably strong sleeper.