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RE: Concrete floor joist HELP

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Since you asked, I will offer what I can, which is precious little, but worth every penny.
My best guess is that Max Jasper is right ... these floors are most likely comprised of inverted precast U-joists with a topping slab.  I would avoid working with them, and becoming liable for them, unless/until the school district can find reliable construction documents.  Beyond that, I plead ignorance, as I was riding a tricycle at the time of the construction.
Thank you for not asking me about sports!
Stan Caldwell in Dallas

The goal of every engineer is to retire

without getting blamed for a major

catastrophe!                      ...Dilbert


-----Original Message-----
From: Brian K. Smith [mailto:smithegr(--nospam--at)]
Sent: Friday, May 02, 2003 3:44 PM
To: seaint(--nospam--at)
Subject: Concrete floor joist HELP

    Well, I need some help again.
    I am working on a building constructed maybe 50 years ago.  The building was originally a shopping center, single story with probably as much basement area as above grade area.  The building was purchased by the school district about 25 years ago, and has been used as a school since.  We are currently making improvements to the school, which include new roof top units, etc.  While inspecting basement, I noticed a floor system that seemed somewhat odd to me.  The floor joist are similar to what I would term "standard" concrete joist, framing into a rather deep joist band beam supported by round columns.  The oddity is that rather than a single joist rib, the joist appeare to be formed as two separate ribs.  They are about 2 1/4" in width, 3" center to center, and tapered on each side with a single big rebar in the bottom of each rib and no apparent stirrups.  The ribs seemed to join in the middle as each one tapered up, and the overall spacing between these joints was about 24".  I was able to remove some of the floor tile on the floor above and never found any type of joint, so I would assume all of the ribs were poured monolithic.  I found an old broken spot in the floor, covered with a piece of plywood, and determined the floor slab is 4" thick with 6x6 mesh; so I have ruled out precast with a topping slab.
    I really don't have to do anything with the floor system (yet), but I would like to know more about it.  The school district is looking for the original drawings and I am going to the city.  Was this type of floor system common 40 to 50 years ago?
    Stan Caldwell what is your FREE opinion.
Brian K. Smith, P.E.