Adding Studs to Existing Composite Beam 3

[PEinVA]

I am adding a large stair to a steel composite building. I am having difficulty getting the existing beams to work. The girder that the beams frame into was overly designed while the beams were designed just below failure at 100 PSF LL. With the additional load even adding a WT section under the beam does not keep the stresses below both 0.66Fy and 0.9Fy checks. Has anyone added studs to an existing beam? I cannot find any information about this and was wondering if it had been done before. Thanks.


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

http://www.tbastructures.com

 

[PEinVA]

Agreed.
Thanks for the logical advice. Its sometimes overlooked.

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

http://www.tbastructures.com

 

[WillisV]

StructuralEIT - yes that is correct, % composite could be controlled by either maximum concrete strength or maximum steel strength. In my experience with typical composite beam sizes, spacing, concrete strengths, etc. the steel tends to control though.

 

[jike]

RCraine:


Although I have core drilled an existing slab and added studs to non-composite beams to increase its capacity, this was done in an industrial environment. It sounds like you are in a commercial environment with your description of a 15th floor. I would probably avoid core drilling because of the difficulty in dealing with water dripping and leaking thru to the floors below. I would elect to add or reinforce beams non-compositely.

 

[SteelPE]

Never having done this before, if you are core drill an existing composite beam don’t you have to be worried about hitting an existing stud? Knowing my luck, every time they drilled a hole they would hit an existing stud.

 

[PEinVA]

SteelPE,
That is my greatest concern. However, lucky for me, there are 14 studs on a 28' span. My guess is at 2' o/c. 50/50 chance, and if we hit one, we can guess where they are. 1 stud won't hurt us if all of this takes place during demo/renovation work.

jike,
I'm confused on your concern about water leaking through levels. Water should not be on any of these levels to being with, and would be a problem regardless if I cored into the slab or not. Is there something I'm missing?

WillisV,
Yes, that is true, if you look at most calculations, the steel is controlling at least 2:1.

Thanks for all the input and feedback.

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

http://www.tbastructures.com

 

[grandcasita]

Water = lube and cool for the drilling operation. They do make containment (and wet-dry vacs) for this so I'd not worry too much about it; it is no worse than containing welding spatter.

We have done this in cases where they tried to laser screed a composite floor and added up to 2 inches too much concrete (even buckling the deck in places before they realized something was wrong.) Adding studs worked just fine.

Some one suggested adding non-composite beams, which sounded like they would place these parallel to the existing to pick up some loads - not connecting it to the existing overloaded member.

You may be able to splice these new beams from pieces short enough to get up to the 15th floor, although at 28 foot span, it sounds like relatively heavy steel sections will be required.

 

[csd72]

You can specify that they use a cover meter to locate the studs, that is assuming that the studs come up to top cover.

As far as bringing in the beams, you can always bring it in in 10' parts and get it welded together on site. 10' should fit in the diagonal of the elevator (get someone to check).

The point regarding water is also very valid.

 

[jike]

Water is used to cool the bit in the core drilling process. You need a sure method to control or prevent water from leaking to the floors below or ruining finishes.