Composite Roof Modifications

[preetis]

My firm is modifying a composite roof. It is a combination of W sections and an 18" concrete roof (36 ksi and 5000 psi concrete with 60 ksi reinforcement). We are adding a series of walkways (tunnels)on the existing composite roof and anchoring it to the roof using anchor bolts. Is there any way I can analyze the additional loads on the roof without really going into too much detail of original composite deisgn? I do not have any experience in designing/modifying a composite roof.

 

[BAretired]

An 18" concrete roof slab? Surely not a solid slab.

I don't have a clear understanding of the existing structure, but it does not sound as if walkways would add a significant load if the existing dead load is high. If you are adding any serious load to the existing roof, you really have no option other than to examine what the existing structure can carry.

BA

 

[MiketheEngineer]

BAretired is correct - check it out..

 

[preetis]

Thats the answer I was afraid of ... but I guess I have no choice. And yes, BAretired, it is an 18" solid concrete slab. I work at a nuclear plant, and the specifications are very strict! Thanks very much.

 

[BAretired]

Well, the existing dead load is in excess of 225 psf. I'm guessing that the live load is specified on the existing drawings. Can you determine how much load you are adding and compare it to the specified live load?

BA