How to intersect two Ibeams.

[Lugnut]

Hello,

I want to add an Ibeam in my household basement. I don't know how to attach it to the existing Ibeam so that they is no lateral movement. I have a mechanical drawing (sort of) showing the setup. It takes 39 seconds to download at 57kbs.
Is it at

http://www.planetkc.com/mchapman/images/Ibeams.jpg

Would someone give me some ideas for attaching my new 4" steel Ibeam to the existing 8" Ibeam to prevent lateral movement of the new Ibeam. There will be little or no load added to the existing Ibeam since the new 4" Ibeam will be supported with its own load bearing steel pole atop a concrete footing.

I want the tops of the two joining Ibeams to be as flush as possible to each other.

This home project application is to build a 8 x 10 ft fallout shelter in the corner of the basement. The new Ibeams will carry half the weight of the new ceiling. So far, the idea is to build a ceiling of 2" plate steel. This provides the needed mass (75 lbs per sq ft) via a low profile without sacraficing ceiling height, while also hiding the hideous steel ceiling.

Mark

 

[Qshake]

To one I beam to another steel angles are often employed. The web of one beam is bolted to one leg of the angles and the other leg of the angles are bolted to the web of the other beam. The flanges of the beam framing into the side of the second beam are usually cut (coped) off to avoid interference.

 

[Lugnut]

Hi, its me again. I need to edit the original post, but don't see how so I am just replying myself.

In the picture referred to in the original post, the new Ibeam appears to be adjacent to the back basement wall. This is not so. The new Ibeam will be 10' from the back basement wall. Thus it will only have two contact points with the existing structure, one at each end of the Ibeam.

Mark

 

[Lugnut]

Thank you Qshake! This solution would require drilling the existing Ibeam as I see it. Would that weaken the Ibeam significantly? Would I drill 2 holes, 1/2" diameter on the larger beam?

Mark

 

[Qshake]

I haven't looked at the drawing. Yes, this will require holes drilled in the original I-beam, a minimum of four - two on each side of the framing member (new I-beam).

Please note that this is only a minimum and someone should actually engineer the connection for approval by the local building authorities.

 

[ishvaaag]

Normally rolled beams have excess safety in shear and 2 1/2 in diameter holes shouldn't affect safety, but it is for this that code checks exist.

It is also interesting to note that except you let the angle connection with the possibility of somewhat slip vertically, any significant load charging on the main beam might buckle the new column if it is weak.

 

[Lugnut]

Thank you Qshake and ishvaaag for the replies.

I hadn't foreseen the possible vertical slip that ishvaaag mentioned and I'm wondering if heavy snowfall or other event could create that condition.

Could I address that issue by cutting a slotted hole in the angle brace at the point where it bolts to the new 4" beam? It seems this might give some room to play by allowing either Ibeam to move vertically. I am assuming that the slip resistance would be less than the buckle resistance of the supporting pole.

If not, is there a fastening technique I could employ that allows slippage if uneven weight distribution occurs on either beam?

Mark

 

[Ron]

Lugnut...I would not slot the holes in a vertical direction as this would require more tension in the bolts to resist. I agree with Qshake that you should consider having an engineer check the connection design for compliance with code.

The issue you bring up is a common connection in steel construction. If you are purchasing the steel from a local supplier who also does shop fabrication, you might ask them for a detail for the connection. In general it will be done as Qshake has described. The angle clip on the existing beam may be bolted or welded to the beam, with its corresponding connection on the new beam, again, either bolted or welded. Since this is residential, I assume you will prefer bolting. Also, if you are doing the work yourself and do not have appropriate drilling capability for large holes, you might consider decreasing the size of the bolts, but adding more of them. Don't use less than 3/8-inch diameter bolts.

 

[Lugnut]

Thanks for the reply. Your suggestions are quite useful. I appreciate the time all has taken for this thread.

Mark