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Old precast plank identification.

Old precast plank identification.

Old precast plank identification.

Residential property concrete floor. It is segmented single hollow core T segments with grout and rebar between the members. The planks are not continuous. Please see the attached section sketch for some rough dimensions. Client looking to remove intermediate wall and I would love a span table to prove it can span wall to wall without extra support. Any help of even a place to look for the manufacturer would be great. Thanks in advance.

RE: Old precast plank identification.

Define "old"?

Are we talking 1930's or 1970's ?

And you are sure it is precast concrete, and not tile or CMU segments?

RE: Old precast plank identification.

1952 per old MLS listing. They are segmented concrete pieces like dox plank. Looks like 6 to 8 ft lengths maybe longer that were grouted at the joints. So you could call them CMU. One area I could see mild rebar exposed, so not prestressed. Chicago land area if that helps anyone.

RE: Old precast plank identification.

I checked out a few of my resources and could not find anything.

I also checked Antiquated Structural Systems Series - Part 5 by Matthew Stuart Link and drew a blank.

You may have to go back to basics and field-determine the actual rebar size and number, and assume a grade of rebar and concrete strength, and check flexural and deflection.

RE: Old precast plank identification.

I wouldn't think that there would be span tables - this looks like a form system.

The "joists" between the forms are simply small concrete beams - like a pan joist system. This would be simple concrete design 101 if you can verify a few things:

1. Geometry of the joists
2. Location, number and size of the bottom bars (assuming simple span).
3. Depth of the bottom bars.
4. Is there a monolithic slab on top forming "T" type joists?
5. Spacing of the joists
6. Rough idea of concrete strength (perhaps some cores taken to verify)...otherwise probably assume 2,800 to 3,000 psi conservatively.
7. Span.
8. Types and amounts of loads on the system from above - self-weight, partitions, flooring, etc. and required live load.
9. Geometry and density of the form system (to add to self-weight of the system for dead loads).

I would then think that the forms are just that - forms - that don't contribute to structural capacity at all.

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