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Adding new studs to existing composite steel beamsHelpful Member!(2) 

olsont (Structural)
6 May 09 10:09
I'm currently working on an existing composite concrete and metal deck floor structure which is supported by steel beams.  My client wants to increase the loading capacity of this floor.  In order to increase the loading capacity, our analysis program indicates that we will need to add additional steel studs to the beams.  Can additional steel studs be add to existing steel beams, how is this done, and at what locations?      
MiketheEngineer (Structural)
6 May 09 10:22
Adding studs to beams??  You mean like an interior wall??

Not sure what you are asking
kslee1000 (Civil/Environmental)
6 May 09 10:28
Interior wall in horizontal position.

No advisale, but I think it can be done. Shore the beam, and core drill the concrete at locations add'l studs needed. Maybe you should change the studs by shapes.
Helpful Member!  JedClampett (Structural)
6 May 09 10:35
This is pretty common.  But it's a messy procedure.  You have to access the beam, which means chipping down through the concrete, until you get to the metal deck.  The metal stud manufacturer allows the welding to be done through the metal deck, but I'm not sure I'd trust that.  I'd want to see what I'm welding to.  Plus, what do you do about the slab reinforcing you've cut?   Nelson (http://www.nelsonstud.com/Portal/)shows some examples in their brochure.  I'd talk to one of their engineers for examples where this has been done.
Meanwhile, do you have total access to the building?  All partitions, carpeting, furniture, etc. will have to be out while this is being done.
Helpful Member!  jike (Structural)
11 May 09 12:32
We have done this sucessfully numerous times in an industrial setting where a little water (from core drilling) on the floor was not a problem. For applications with in place finish material or electrical, I would probably consider other methods because of the water used for core drilling.
frogit22 (Structural)
21 May 09 16:37
This is not uncommon, but consider your new studs will only help in accepting additional live load (dead load is already being supported by existing structure).   
RCinVA (Structural)
26 May 09 16:02
Could you just add a plate on the bottom the beam instead?

RC
All that is necessary for the triumph of evil is that good men do nothing.
    Edmund Burke

 

darthsoilsguy2 (Geotechnical)
17 Jun 09 0:45
maybe plating up the beam flanges so they act more like hollow-shaped steel?
AHaddad1 (Structural)
28 Jun 09 8:26
I have successfully used the coring method from the top and the addition of studs as needed on a roof system to increase the live load capacity of the roof (originally the roof beams where designed as non-composite), just be carefull when adding the stresses to calculate the final stresses. The dead load stresses should be calculated based on a non-composite system and the live load stresses based on the composite system and then added together to compare against allowables.

After coring the holes, the studs are fused into the steel beams/girders in the center of the core, care shall be taken during the coring operation so not to core the steel beam by mistake (the holes should be inspected for that prior to grouting the holes), in some cases forming will be needed from the underside to be able to pour the grout, it all depends whether the core hits the top or bottom flutes or in some cases both deck flutes at the same time.

Hope this helps

A
AHaddad1 (Structural)
28 Jun 09 8:48
If you decide to add a plate to the bottom flange, then add two angles to the underside of the top flange on either side of the web and weld the end of the angle legs to both the top flange and the web of the beam. This can easily be done for the beams; however, cannot be done for the girders due to the intersecting beams at the girders.

A combination of adding a plate (at the bottom flange) and two angles (at the top flange)for the beams and coring studs for the girders might not be a bad idea.
jike (Structural)
10 Jul 09 8:48
Adding a plate to the bottom will help lower the CG in the beam and thus increase capacity. The plate on the bottom helps balance out the area of the concrete slab on top. It is unlikely that you will have to add angles to the top flange.
AHaddad1 (Structural)
12 Jul 09 7:42
Jike, in my post I am adding the top angles only if the beams stay non-composite without the added studs. For the girders the addition of the top angles is difficult because of the intersecting beams; therefore , requiring the addition of studs if so desired to move the neutral axis up under superimposed loads.
hokie66 (Structural)
12 Jul 09 8:00
Adding two angles under the top flange of a beam sounds very tricky.  How would the angles be oriented?  What size would they be in relation to the flange width?
AHaddad1 (Structural)
12 Jul 09 8:45
I have used it many times, I do not have a scanner at home to draw a sketch and link it for you, I will try to describe it.

say for example your beam is a W16x26 which has ~ 5.50 inch wide flange and a web = 3/8 inch thick.

The projected flange width on either side of the web would be ~ 2.6 inches.

In this case you may use a 2 - 2"x2" angles x whatever thickness you need.

The vertical leg of the angle will be 2 inches away from the web and the horizontal leg of the angle will be 2 inches below the underside of the top flange.

Use field filet welds (one sided) to the accessible welded face between the vertical angle leg and the top flange, also between the horizontal angle leg and the beam web.

Hope that clarifies the retrofit.
dik (Structural)
12 Jul 09 12:06
You can take advantage of 'pre-flexing' the beam to improve camber and moment/stress distribution across the section.
hokie66 (Structural)
13 Jul 09 0:33
AHaddad1,

I've never done it, but at least now I understand what you mean.

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