OWSJ with Concrete Roof Slab

[murphy89]

Hi there, was on a site this week with OWSJ framing between larger steel trusses. The joists support a v-pan and concrete roof slab. Pictures are attached. Apparently, this was built in the 80's. For context, the joists are 12" deep @ 2' spacing, and the trusses are 5' deep @ 8' spacing.

I haven't seen this framing combination that I can recall. Would the concrete be designed to span one way between the OWSJ or would they be there to support the roof when it's curing and now the slab spans 2 ways?

Also, any thoughts on what the plastic mesh under the v-pan is for?

Thanks!

 

[jayrod12]

Plastic mesh could be an early form of acoustic treatment. The slab would normally be designed to span only between joists. The joists then span between beams.

 

[KootK]

One way. It would take a very thick slab to compete with the stiffness of the joists in the direction that they span.

 

[murphy89]

Thanks for the responses!