Burnt openings in Channels

[Titleist.Guy]

Hi all and Happy New year!

So, I came into today and walked through the site, and found quite a bit of this, (see attached photo).

The problems here are pretty obvious:

1) Non-engineered web openings
2) Torch cutting these holes

My question, to the best of anyone's knowledge does the AISC DG#2 extend to any other shape besides W flange? I'm assuming it does not. Intuition tells me that with the shear center being off the shape already, and now removing the middle(ish) portions of the members, that we're going to see a different response in the member due to the openings. The problem is, I can't find any literature on web-openings for channels. I've gone through the Modern Steel steel-exchange archives, scoured the net, and re-read the AISC DG#2. The closest I'm finding is a very little info on cold formed steel shapes. I'm looking for any advice or wisdom that anyone wants to share before I go lay into the contractor, and their engineer.

The loads are reasonably light -- however, if we use the DG#2 as a benchmark, then I think we're in a bit of trouble:
I know that several of these shapes are likely not compact,
In several locations the point loads are dead nuts over top of the opening, which wouldn't even fly if it were w-shaped members,
Also, many of the geometric recommendations in AISC DG2 wouldn't even apply here, with respect to opening ratio limits, and hole sizes,
The holes that were burnt suffer from 'beaver chewing', with many edges longer than 3/16" b/c no one ever went back to grind those smooth,
And if we wanted to add some 'token' reinforcement, there wouldn't even be enough available section left to attach to.

Now, not all the holes are created equal, some are much smaller, not pictured, and are possibly reinforce able, but this goes back to my original question, I can't find any reasonable guides in the literature. Part of me thinks putting 'back' the amount of section that was removed via bars or cut pipes welded around the holes might just be the solution, but I frankly don't know.


Anyway, I appreciate anyone who took the time to read this and any insight would be great.

Thanks!

 

[Titleist.Guy]

Another picture -- and yes that's very much an oval looking circle.

 

[Titleist.Guy]

One final picture.

Thanks again all!

 

[JStephen]

Just curious- it looks like those are cut for pipe or conduit. Were there drawings that showed pipe and conduit were to go there, rather than, say, below the channels?

 

[JLNJ]

It looks awful but not oh-my-God horrible. It all depends on the loading on the channels and the stresses therein.

 

[Tmoose]

The low resolution pictures are not as useful as they might be, but it looks to have been a nicely detailed and finished installation before the sooty holes were added.

The services "craftsmen" who cut those holes should DEFINITELY be prevented from running their pipes, wires or ducts until the holes have been approved by the Engineer of Record.

It would be a real shame if the repairs the Engineer of Record requires to restore the designed strength and performance of the floor are not done with workmanship equal to the original installation.

I'm guessing the requirements will end up something like the rules for wood joists in residential construction. The maximum allowable diameter of a hole in any solid-lumber joist is one-third of the joist’s depth. The holes must be more or less centered on the face of the joist. Notches aren’t allowed in the center third of a joist’s length. Those centered holes can be drilled anywhere along the length of the floor joist provided there are no other holes in the joist or notches along its top or bottom.

 

[TEDstruc]

1. Which car plant is that? Just curious.
2. I don't know of any specific references for looking at holes in channels vs W-shapes. But I have run into this before, and ended up having to revert to engineering judgement.
3. It looks like some of those holes might be burnt through back to back channels, bolted together. One might be able to make the argument that they behave like a W-Shape.
4. If you determine that you have to reinforce the single channels, you might be able to weld a channel of the same size with a shop punched hole to the back face of the existing channel. On the existing back to back channels, you could add some some form of welded collar around the burnt hole.
5. On those type of screen guard frames, usually the outer single channels see very little load, and the back to back channels carry most of the load, but it of course depends on the framing layout and loads imparted on the frames.


Best Regards

 

[JLNJ]

There are plenty of design methods out there for these types of holes.

The AISC has a published Design Guide for this exact purpose. No need to guess.

 

[KootK]

1) It's been a while since I've looked at the AISC design guide but, by and large, I would consider the WF provisions applicable to channels. I doubt that would work though given the size of your holes relative to the depths of your members.

2) Given that your shear demands are likely very low here, you might be able to justify the situation as is by doing a Von Mises combined stress check on flange/web junction to see if that alone can give you the shear resistance that you need.

3) AISC's relatively new design guide on Castellated beams may well be an applicable source for this. Still WF.

 

[Titleist.Guy]

All,

Thanks for the thoughtful replies.

I'll try and go down the line here...

JStephen -- You would think right? Unfortunately in these big plants during our short shutdown windows we have 1200+ workers spread throughout several dozen disciplines, unions, and so on, and little if any coordination is done. I asked the same thing ... doesn't anyone look at TOS and pipe invert elevations?! But everyone thinks their task is the most important and little if any coordination is ever done with us to that end.

JLNJ -- Agrred, the loadings are relatively light, its the fatigue issues, and the 'plant factor' (what I like to call it), which just means that assume that any piece of steel hung will at some point be used inappropriately and therefore adding holes in the members just cuts into the safety factor that much right off the bat.

TMoose -- Yes, the pics are not the greatest, but they came to me from my 2nd shift guys, and they were good enough to deliver the point, I went and walked it all down around 3am that morning after I got the call and its worse than it looks. We have very explicit language in our specification regarding modification of existing steel and the requirements of needing PE approval, calcs, and owner buyoff. I've already delivered the point that not only will it be repaired, but they will be repainted afterwards.

TEDstruc -- Which car plant -- A pretty important one. You are correct in your assessment, some holes are in just channels, probably 75% or so, some are in the transition panels between modules which would the be bolted back to back channels, and there are a few random Wide flanges that got modified as well. And yes, your point on load path is correct. The outboard channels don't see that much load and that is being considered in the repair detail.

JLNJ -- I'm not sure if you read my entire OP, I already referenced the fact that I did reacquaint myself with the DG2 and that the entire premise of my question was applicability of those methods to non doubly symmetric members. To that point, here is the response I got from AISC:

The scope of Design Guide 2 does not explicitly limit its use to wide-flange shapes. However, it does repeatedly refer to the remaining sections above as “tees”. Based on this the guidance provided may not be directly applicable to channels. You would also have to account to the taper in the flange of S-sections in some manner. Ultimately you must use your own judgment.

Please let me know if you have any further questions.

Larry S. Muir, P.E.
Director of Technical Assistance
American Institute of Steel Construction
866.ASK.AISC
cl/eng


KootK -- I've already ordered DG29-34(?), or whatever that latest batch is, as mine currently only go up through 28 I believe. I did visit some cellular beam company pages to review their specification literature, and I have yet to see anything but a Wide flange shape as the basis of their designs.

Having said all that -- I met with our general contractor's PE, the gentleman in charge of the solutions here, and we've agreed on the following. First, we're going to add approx. 1/4" to the radius of each hole, to account for the burning of those holes and the chewed up sections. This essentially makes each hole 1/2" bigger in dia for analysis.

Second, we're approaching this from a perspective, similar to the Chapter H equations in AISC 360 - we're going to look at Vn, Vu, Mn, Mu, at their respective ratios, add them up, and use some engineering judgment on whether or not we can skip reinforcing. Potentially setting a threshold around 0.25 combined utilization as a test. Anything over, we'll reinforce, anything below we 'may' live with.

Third, the repair itself will likely be just putting back what was taken out vis a vis adding plates, and just ensuring that we have enough plate length to provide enough length to develop our welds. The intent is to make sure the plates are as symmetric as possible. We're not going to worry too much about the COG of the reinforced member as I'm expecting almost no axial loadings.

Fourth, after surveying all the holes, the direction I gave was to envelope the biggest hole sizes and shape sizes, schedule those out, and issue a small handful of repair details into as few typical details as we can, so that we can give to our millwrights (or ironworkers). All they'll have to do is measure the hole size, add a half inch, look at the member depth, and pick either detail A,B or C kind of thing.

At the end of the day being the owners structural PE is tough because I have to balance making something into a science project and doing the right thing vs. hitting our start up dates, anyone that has experience in this automotive will understand. Its VERY challenging, getting people to focus on the building, when all everyone really seems to care on are the widgets we make, and not the building we make them in.

My biggest issue, is the fact that those holes exist period -- people will now see those, and take that as some sort of tacit approval to mutilate our steel to make way for their MEP or whatever else they need to run. In addition, torch cutting and burning the steel is a massive no-no and that message is also going to be conveyed by those holes as well. Hopefully after everything is reinforced and painted it won't be so apparent but anyone looking for a shortcut will find one.

Thanks for the feedback everyone.

 

[Titleist.Guy]

KootK,

Part of me wants to think the provisions apply to channels, same as WF, but something in my guy tells me that it doesn't. When I read through the DG2, a lot of their formulation revolved around equivalent sized T shapes, and symmetry and so forth. I'm weary to take an apples to apples approach, and was frankly shocked that I couldn't find anything really in the literature on this. On the bright side I am looking forward to getting my shiny new DG's in the mail soon.

 

[Tmoose]

So those holes both in nominal size and number ARE required to run some services ?

 

[Ron]

Guys...y'all are thinking this thing to death! Good discussion, but don't expect AISC to always bail your asses out! Use your quite-capable engineering capability and judgment, reinforce the openings and move on.

 

[Titleist.Guy]

Tmoose -- Yesir, they cut those for fire protection. And yes, at other plants I've always been a fan of just running the fire protection on the screen guard, dog housing it, stripping it for trip hazards, and putting the drops through the guard, but in this case the FP is ran dead nuts under the centerline of the overhead power and free.

Ron -- Your comment is noted, and reflected in the fact I said I don't want to make this a science project. Also, I'm not expecting anyone to bail me out, however, I also feel compelled to do due diligence as well, so its very appropriate in my mind to pose the question. If you like shooting from the hip more then by all means, (which is more my style to be honest), but I also need to make sure before I throw a monkey wrench in the schedule that I've looked into it.

 

[racookpe1978]

Problem with "hand-burnt" "holes" comes in three parts: You've addressed one of them.

Loss of WF or CH or WT/ST capability by the opening. You're addressing that.

But also: Irregular opening makes the theoretical calc very hard: Not a circle, not a uniform ellipse, not an oval, not a square or rectangle. Adding 1/4 inch helps the approximation attempt, but the irregular position of each hole means every beam has to be re-calculated for actual loads and actual impact of the analysis.

Crack risers, stress risers by the scars and irregular edges of every inch of the burnt perimeter. If the beam is under POTENTIAL vibration or flexing, grind smooth the burnt remnants, then grind smooth the edges of the hole to be sure no cracks will initiate from stress risers and gouges. Flexing that remains all tension or all compression (not back and forth) is usually less severe.