CIP Floor on "Fabric" and Steel Joist

[jheidt2543]

I have run across a structural floor system I have not seen before and I'm looking for design information. I have the architectural drawings dated 1953, but no structural drawings. The system is composed of 10" deep "light" steel joist labeled #102SJ with what looks like a light gage steel mesh over the top, then a fabric of some type, on which is poured a 2-1/2" thick normal concrete mix for the attic floor (See attached photo).

The system is used throughout the building, but in the area of the photo there seems to be much more deflection of the fabric. I'm trying to determine if this is normal or if the area needs to be reinforced. There have been no noticeable problems during the life of the building - so far.

Anyone know what system this is and where I can get design information or load tables?

 

[dcarr82775]

Is there wire running perpendicular to the joist span as well? The pic shows wires parallel to the joist span, but not clear what happens the other way.

I have seen similar systems with something like an expanded metal lath and some paper. It always sags noticeably, but not quite as much as your picture shows. The systems I have seen are many many decades old and survived office/restaurant/retail use. I have always left them alone if the system shows no signs of distress. I will take measurements on the joists (I have not run across the type of web yours have) to get a feel for their capacity, but I tend to leave the slab alone.

I have not references on their design.

 

[jheidt2543]

Yes, the wires of the mesh run in both directions, you can see some of them on the far right of the photo. The mesh wire is in a rectangular pattern, not square. This must be some type of engineered system, because the joist are so light, there is also a diagonal bracing system, which you can see in this photo; they happen to all go in one direction. In other areas they are x-braces. Oh, the joist are at 24" o.c.