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Re: Steel beam connection detail

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Billy,
Are you strengthening the slab to increase its flexural strength only ?  In other words, is the punching shear capacity sufficient or does it need to increased also ?
I have strengthened some slabs by adding small steel beams to the under-surface, bolted to achieve composite action.  Actually, I used short segments of steel W-sections between the concrete and the added beams to avoid the electrical conduits on the ceiling, and increase the depth to the added steel, something like a stub-girder.  The short segments are welded to the new beams, and bolted to the concrete.
If you have sufficient punching-shear capacity, you don't really need to connect the new beams to the columns, although I would do it anyway.

If you use short segments with a height about equal to the drop thickness, you can simplify the problem a little.

Kevin


On Sun, May 25, 2008 at 3:12 PM, Harold Sprague <spraguehope(--nospam--at)hotmail.com> wrote:
There are a lot of variables to your request. 
 
Strengthening drops is not all that uncommon.  You could consider slotting the concrete and adding in a stud rail and then grouting the slot.  I would not attempt this without shoring the slab.  There will be a lot of rebar that will be in the way. 
 
Placing a steel beam cantilvered from the colum is difficult because of the tension component.  A possibility would be to drill through the column and place threaded rods through the column.  Provide a tube welded to the under side of the beam, run the threaded rod through the HSS so that you can transfer the tension and preload the rods to transfer the shear in the welds and then to tension the top flange. 
 
The steel beam will occupy some finite distance below the drop.  I would consider just forming up a deeper drop and consider using SCC.  You may also want to consider removing the existing drop and forming up a new drop using SCC.  You can get 8 ksi SCC without a lot of hassel.

Regards,
Harold Sprague



Date: Sat, 24 May 2008 09:12:31 -0700
From: s3ndy_121.civil(--nospam--at)yahoo.com
Subject: Steel beam connection detail
To: seaint(--nospam--at)seaint.org

Dear All,

I need your help on the case below:

Steel beams are used to strengthened flat slab with existing drop panel. How to detail and design the connection between steel beam and column with drop panel where no haunch below the beam is allowable.

Thank you

Billy



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