×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Ribbed concrete roof slab w/CMU infill?

Ribbed concrete roof slab w/CMU infill?

Ribbed concrete roof slab w/CMU infill?

(OP)
I am investigating a roof design that I have not previously seen.  The roof consists of a 2.5 in. slab cast with 6"x12" RC beams spaced at 21".  Between the beams are 12"x8"x16" hollow core CMU blocks.  I assume the CMU was cast with the concrete and are anchored in some fashion.  My question is what was the purpose of adding the CMU, resulting in a large DL on the roof?  Is the CMU providing any structural contribution?  

Kelly Lyons, PE
Principal
www.sTrucTure-Tec.com

RE: Ribbed concrete roof slab w/CMU infill?

It might be a variation of this type of system:

http://www.aircrete.co.uk/buildingwith/floors.htm

where the cmu turned sideways is slid into place and supports the floor.  The cmu is then supported by beams at each end.  I remember a web page that had a system designed for cmu but can't find it now.  This is just a guess that came to mind.

RE: Ribbed concrete roof slab w/CMU infill?

If its a fairly old structure, past practice included using masonry as a form fill between joist ribs.  A flat system of formwork was constructed first, with the masonry just loose-stacked in a fashion to form the continuous joist ribs.  Then the joist reinforcing was added and then the concrete placed.

The masonry, having irregularities, holes, etc. would be interlocked with the concrete such that when the formwork below was removed, the masonry just stayed put.  Then you'd end up with a flat surface that could be plastered without constructing a secondary ceiling support system.

RE: Ribbed concrete roof slab w/CMU infill?

(OP)
Yes, it's a structure build in the 60's.  Your discription matches what I am seeing.  Thank you both for your reply.

Kelly Lyons, PE
Principal
www.sTrucTure-Tec.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources