Bored holes in steel support beam.

[andy32821]

Hi Guys,

I need to cut a couple of (1" ?) holes in a 12 inch square steel support beam and fish FMC. Where do I find the limitations on what size holes I can drill into this beam? Is there a limit on where in the beam I can drill.
This is in Florida.


Thanks,
Andy

 

[roger]

Codes are not really the place to look for this, you need to consult with a structural engineer before you drill/cut any size hole in one of these beams.

There is probably no problem but you don't want to make this discission on your own

Roger

 

[tshea]

Absolutely contact a structural engineer. Get it in writing that it is OK.

Is there any other route??

 

[petersonra]

I suspect if you look closely in either the job specs or the plans, some mention will be made of just what you are allowed to do as far as cutting holes in structural elements.

If not, contact the architect who can tell you what is allowed (assuming it is a relatively new building).

 

[Paul B]

Is it a vertical or horizontal beam?

 

[andy32821]

Hi Guys,

Thanks for the help. I was hoping this was covered by a general engineering guideline. I went through the specs. Not much help. But the existing supports are welded or 1/4" bolts.

The customer said he could live with exposed conduit rather than pay an engineer. (Very demanding people seem to melt when it comes to putting out cash.)

This is a vertical beam. If there is some type of generally accepted engineering guideline for this sort of thing please let me know.

Thanks,
Andy

 

[steve66]

I think the generally accepted practice is to go around beams - not through them. It's going to be a bear to drill through anyway.

Steve

 

[spsnyder]

I don't think you should drill any holes in the beams. However, if you were to drill a hole in a joist the best place structurally is the center of the joist and closest to a column or wall. I don't know how many times I've seen holes drilled in the bottom (or top) of a beam. Makes me cringe. FYI, The reason the middle has the least adverse structural effect is that the top of the joist is under compression, and the bottom of the joist is under tension. The center has no strain, therefore a hole here has less effect on the structural integraty. That is why an I-beam is designed the way it is. The the tops and bottoms have much more steel to increase the load it can handle. That's a simplistic explaination but hope it helps. And maybe it will result in a few holes being drilled more toward the center of a joist in the future. Best of luck with the client.

 

[Paul B]

Also the flanges on the I-beam keep the web from crippling.

 

[ramdiesel3500]

I'll tag onto spsnyders comments. I have some background in structural engineering and stress analysis. Stay away from the flanges when it comes to drilling just as stated above! Also, when drilling the web of a beam, always stay near the center (vertically) and also try to stay near the middle third of the span. The web sees a good measure of shear stress near the ends of the beam and holes in the web increase the shear on the remaining material!

 

[don_resqcapt19]

I think this is really a square steel colunm and not a hortizontal beam.
Don

 

[andy32821]

You ar correct. Sorry for the lapse.

It is an exposed vertical square collum 12" on each side. The customer wanted the conduit hidden from view, so I was going to take flex in the top and out the bottom. But with no engineering guideline or code to fall back on, an engineer would be the easy way out.

Lucky for me this was not a fixed cost job.

Thanks,
Andy

 

[hardworkingstiff]

1st, I'm not an engineer nor do I have any training in the field on engineering.

Now that this disclaimer is out of the way, I've wired a lot of gas stations. They use 8" - 10" columns to support the canopy. It is very common for them to cut holes in the columns (near each end) so a 3" PVC drain pipe can enter/leave the column.

I've alway heard the support for these columns are in the 4 corners and it did minimal damage cutting into the flat middle portions. If this is true, I see no problem in drilling and flexing like you mentioned, but paying an engineer to sign off on it would be wise.

Others (in the engineering field) can correct my understanding.

 

[iwire]

1st, I'm not an engineer nor do I have any training in the field on engineering.

I see no problem in drilling and flexing like you mentioned,

I agree with Hardworkingstiff.

Unless the structure had some very unusual design to it I would just go ahead with a 1" hole centered in a 12" square vertical column.

 

[Paul B]

Columns are designed to resist buckling. The radius of gyration is used to determine the stiffnes of the column. Also the slenderness ratio comes into play. Drilling a hole in a vertical column in most cases will not effect the integrity of the support. If the column has gussets coming back into it it creates a whole new ball game. Gusset do funny thing to columns that is why most folks design them out.

 

[LarryFine]

. . . if you were to drill a hole in a joist the best place structurally is the center of the joist . . .

Right.

. . . and closest to a column or wall.

Wrong!

The middle third in both directions is the safest area to penetrate.

 

[growler]

Drilling holes in a material actually makes it stronger. There is no technical explanation for this phenomenon but have you ever noticed that nothing will ever tear along the perforated line as indicated by the instructions. ( It's an old joke but maybe some of the young guys haven't herd it )

 

[davidv]

I guess if it aint carrying much load like a roof and only one out of the many coulmns wont hurt a bit.
if its an inch hole, maybe yud like 2 use an acetelyne torch, much faster & will save ur drill life. a smaw is harder to control, better left to some golden hands

davidv
es

 

[spsnyder]

Quote:
. . . and closest to a column or wall.

Wrong!

The middle third in both directions is the safest area to penetrate.

Larry,

Are you sure. The largest moment on a horizontal beam is in the middle of the beam. The closer you get to either support the less the moment.

Thanks.

 

[Paul B]

Closer to the end supports the greater the shear.