HSS10x10 Column Dents
HSS10x10 Column Dents
(OP)
Hi All,
KookK had a great thread last year about column dents, and I've run into a similar issue, but I'm thinking this one merits some repair. See below pics.



It's a 40' tall HSS10x10x3/16 in 50' square bays with a TPO roof, ie very light. The bottom 4' are what you see. Column appears plumb as I put a level on all sides.
Here are my repair thoughts, weld 3/4"x4" studs at 12" o/c on each side and encase it with concrete, either 2' diameter or 2'x2' square pier that has stirrups and vertical bars that are epoxy anchored into the "pier", ie concrete to fill slab cut out, below. My thoughts are that that will stabilize any buckling opportunity and transfer load as required.
Problem is, I don't feel like I can "design" check this. It's just judgement based that load can transfer to the studs around the bent areas and then back into the column at other studs and it will stabilize buckling etc.
What blinds spots do I have?
Thanks to all!
KookK had a great thread last year about column dents, and I've run into a similar issue, but I'm thinking this one merits some repair. See below pics.



It's a 40' tall HSS10x10x3/16 in 50' square bays with a TPO roof, ie very light. The bottom 4' are what you see. Column appears plumb as I put a level on all sides.
Here are my repair thoughts, weld 3/4"x4" studs at 12" o/c on each side and encase it with concrete, either 2' diameter or 2'x2' square pier that has stirrups and vertical bars that are epoxy anchored into the "pier", ie concrete to fill slab cut out, below. My thoughts are that that will stabilize any buckling opportunity and transfer load as required.
Problem is, I don't feel like I can "design" check this. It's just judgement based that load can transfer to the studs around the bent areas and then back into the column at other studs and it will stabilize buckling etc.
What blinds spots do I have?
Thanks to all!






RE: HSS10x10 Column Dents
I did a similar repair as you mention with a round tube (10"OD): I added studs, i wrapped it with a 18"(?) pipe halves-welded, i filled it with concrete. I designed my studs to transfer the vertical load of the column into the concrete above the dent and 'around' the dent.
Edit:
Also, suggest painting more of the column and possible bollards to keep the forklift driver from hitting the repair... maybe dangle a tennis ball from the ceiling?
RE: HSS10x10 Column Dents
Thanks much, and I can fill the column. They also want the protection, so I'm thinking just form up around it and place concrete, or a steel pipe welded would be great too if they want to spend the $.
I feel bad for the next forklift driver...
Interestingly enough also, they asked me for a "repair" option and "protect" option. I can't see a simpler repair than forming it with concrete since they want it protected too. Only other option I see with steel is for them to temporary shore, cut out the bad piece, put in a new piece and full pen weld it. And even then, I don't know how you get backing bars in there to do that and I think you would need them per AWS wouldn't you?
RE: HSS10x10 Column Dents
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
RE: HSS10x10 Column Dents
Mike McCann, PE, SE (WA)
RE: HSS10x10 Column Dents
I think that the steel sleeve will add more protection from impact than just concrete surface, the concrete will get chipped and hammered by forks, the steel sleeve filled with concrete will ding, scrape, but will only fail when it shears off the entire system...
Have fun!
RE: HSS10x10 Column Dents
If you presented the client with a concrete reinforcement scheme and a steel reinforcement scheme for them to price, I have a tough time seeing them choosing the concrete option unless they'd been biased towards protecting the snot out of the thing. Consider the work required for both schemes:
Concrete Reinforcement
1) Mobilize a stud welding machine to come out and do just a handful of studs.
2) Order a large, uncommon steel tube segment and have it cut in two in the shop.
3) Demo the slab on grade if OP decides to implement that.
4) Perform a vertical orientation full/partial groove fiel weld of the tube halves.
5) Cast non-shrink concrete around the outside of the column.
6) Drill a hole in the column and fill it with non-shrink grout.
7) Weld a patch over the grout hole if you're inclined to do so.
Steel Reinforcement
1) Order of few length of some common material that will be lying around any local shop.
2) Fillet weld everything in place.
3) Wait for your fence thingy to show up in the mail.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
Great points. So my concern with your channel detail are:
1. I think the tube column is already too bent out of shape. There isn't a straight side to put in the flat plate. It's bulging both sides.
2. I don't want to bear the channels on the concrete below in order to transfer that load. the damage extends low on at least one of the two affected columns. so I might not be able to develop the plate on either side.
With that said I like your detail and am open to other suggestions.
Also, one other question in terms of HSS shape splices (can't work hear because of constructability), but don't you have to have backing bars if you did a full-pen weld?
RE: HSS10x10 Column Dents
The steel sleeve is dead easy and simple, and I don't even believe the studs are required. The steel provides excellent restraint for any bursting stress. And the impact resistance will be much superior to either just concrete or steel shapes.
RE: HSS10x10 Column Dents
Thanks. Problem with full-pen welds and backing here is that you can't put a new piece if there are backing bars in the way because it wouldn't fit on the existing column. Unless I'm missing something?
RE: HSS10x10 Column Dents
RE: HSS10x10 Column Dents
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
Bah! I set my original detail up assuming that the flexibility of the the flat plates would allow you to "hug the curve" as it were. The sketch below shows how you might handle it in a more extreme case. If you can find 4" of decent column above or below the damage, you should be good to go.
No, certainly not. Again, you only need a small amount of healthy column at the bottom to get the job done. How about a pic of the column with the lower damage?
I question this. Baring a vary long sleeve, without the studs I would expect the compression to remain in the steel section. And I wouldn't trust internal grouting to prevent further HSS wall buckling given:
1) How the extreme dents would push into the grout.
2) That grout shrinkage would probably crack the grout right behind the dent.
3) That the grout above the dent could be forced upwards.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
I really like both of your details, so I'm going to give both options. KookK, after further inspection, I think your first idea can work. And, if it can't based on field dimensions, surely the 2nd detail can. What do you guys think of the below? I'm thinking I don't need to had rebar to the concrete filled section because it's already confined, but I'm open to ideas.
As for the other detail, by my calcs, on a 40' column I need about 71kips of ASD load. The controlling welds are the vertical flare bevels which I calc at 70ksi*0.6*(2*3/16*5/16 eff throat)*8"long*4total welds/2(omega)=78.75k capacity of weld. The fillets on the 1/2" plate and c15 are a slam dunk.
Only other thing with KookK option. what do you think about the moment capacity being compromised and impacted the KL/r ratio above, etc. I'm not really sweating this in this instance, but curious how a somewhat weak link might impact.
Disclaimer to any future users of this detail, it's not Finished, preliminary!
RE: HSS10x10 Column Dents
RE: HSS10x10 Column Dents
Now, in the real world, it will likely go into the diamond cutout of the slab that bears on the footing below, but there is a load path other than that. Does that make sense?
RE: HSS10x10 Column Dents
1) I my original detail, I'd intended the flat plates to go the full height of the repair which would address the kL/r issue. Because the damage is so low in the column, however, it's probably not important here.
2) I'd hold the steel up 1/2" from the SOG.
3) Why's the steel repair so tall? Seems like it could be about 2' long centered on the damage.
4) I worry a bit about vertically restrained shrinkage craching in the concrete. Perhaps bond with the inner and outer tubes us enough to deal with that. I'd be tempted to specify a low shrinkage mix.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
With your detail, would you see any problems with welding perpendicular to the face of the HSS Wall on the only walls that are probably supporting 100% of the axial load; similar to transverse to a flange of a W-Beam in highly loaded condition? And then 4-times.
I don't even think that a PJP weld is 100% necessary. One doesn't need 100% of the compressive strength of a composite steel section, a simple chamfered edge and fillet-groove or something should be more than sufficient for a sleeve... or am i missing something?
Concrete just allows for more construction tolerance and unless you have a highly detailed 3d measured deflected column then you run the risk of things being skewed.
The way i view the column-repair, maybe likely in error, the column is holding itself up now (maybe no safety factor?). I want to support the damaged area so it does not deform under new loads, i want to take any new load, and i want to restore some of the surplus capacity (safety factor). What ever accomplishes that great. Concrete takes load, keeps it from moving downward (if it cannot move down it cannot buckle inward), and if i make a big enough ring/box i don't care if the column i out of plane by 2" vs 2.5". I have reinforced dents with big L angle columns welded on the sides of the column beyond the dent to keep the column from deflecting down... it worked well and your detail is similar but with more welding (required for degree of damage)
RE: HSS10x10 Column Dents
I would maybe add some studs in the middle of the column, including the damaged area to help keep that area from moving inward (yes tension of concrete)
I'd specify non-shrink non-expansive fine grout for the concrete.
Maybe slope the concrete at the top to keep people from spilling their sodas on the concrete flat surface
KootK's, Should you cap this thing with something? keep the top closed off?
RE: HSS10x10 Column Dents
It's certainly worth of consideration:
1) In my original detail, and the one that I recommend if it's possible, there would have been full height flat plates and no transverse welding.
2) It's somewhat of a different situation than with a wide flange beam.
2a) Your axial stresses in such a slender column should be no where near those in a beam flange.
2b) You've got four sides sharing the load. You can rotate the welding with some cool down time in between.
2c) Softening a beam flange can lead to flexural deflection in the beam under load. Less of an issue in a column.
3) Now that I think of it, one could do parallel welding with the stitch plate option as well. And that would be an improvement.
If the look would be acceptable, you could just fillet weld on a radiused splice plate.
Non-issue. It's just fine if things are skewed.
Maybe for aesthetics but certainly not for structural purposes. There's no doubt that the concrete solution is prettier and cleaner when all is said and done. My only beef with it is the cost.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
1. The reason I opted out of Parallel fillet welds as opposed to flarebevel at the corners is because the bottom plate has to be so close to the bottom that I didn't think it would be constructible to put a fillet weld that close to the floor.
2. Reason for the height is that some of the damage extends to nearly 4' on one of the columns. Not sure I posted that picture.
3. I think I'll show a vertical rebar in between each pair of studs to accommodate shrinkage based on 0.0018*area. As well as spec non-shrinking grout fill.
4. I might add a layer of studs at the damaged area too just to "hold" it in place. Belt and suspender approach.
5. I get the concept of holding it 1/2" off the concrete, but my thought is that if I leave it flush, it's just one more load path in the case of emergency. Theoretically I get the not wanting to load the slab infill, but if this column were to ever experience an overload, it would at least have somewhere to go, albeit "junky" fill-in concrete. Are there other downsides im not thinking of?
RE: HSS10x10 Column Dents
In your steel detail, I would make mention of the fence thing as part of your recommendation. From an industrial engineering perspective, I'd think that you'd want something in place to keep folks from bumping into the sharp corners with their bodies, not just their forklifts.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
RE: HSS10x10 Column Dents
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
I appreciate the back and forth as always! Have a good weekend (if those exist for you)
RE: HSS10x10 Column Dents
It would be bold but I'm pretty sure that you could do a sonotube concrete wrap with a column cage and everything would be just fine. No casing, no studs. I've seen some composite column stuff and driven pile / pile cap research that leads me to believe that you cold fully develop the tube into the concrete in about 15" of embedment, even without the studs.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
RE: HSS10x10 Column Dents
The one on the right grabs me. I would make sure those welds on the half pipe are complete penetration by using backer bars. The pipe is there to restrain the core, not carry the vertical load.
RE: HSS10x10 Column Dents
I was assuming this to be an industrial facility not the elevator lobby at Louis Vuitton.
Based on anything other than this vague experience stuff? At the end of the day, it's just steel like the column itself. An integral part of the detail is, of course, the protection fence that has been mentioned several times.
I'd argue that the fence actually provides better protection than the concrete encasement. Every time that a forklift runs into the concrete, you've got potential for more steel damage immediately above and below the concrete. And now that the obstacle is twice as big as the original column, you're likely to have that many more impacts, each tending to batter the anchor bolts etc.
How much restraint could this lightly compressed concrete core possibly need? It's not as though it's the plastic hinge at the bottom of a moment frame or anything. By Nick's numbers I get about 3 MPa factored on the concrete section. I'd be happy to flange bolt the two halves together if that would't just result in more sharp edges.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
It's industrial space, so I don't care too much if it's ugly. And, they are going to bollard around it or put in some other bumper system to protect it. But if it happens again, they can fix it as such as time as that.
Agree on the CJP weld for the half pipe. Ultimately, they both work structurally, but as KookK brought up, one is just significantly cheaper than the other. I would prefer a slate roof for my house, but the asphalt shingles still work.
RE: HSS10x10 Column Dents
I'll only respond to the "vague experience" bit. It amounts to about 30 years, from aluminium smelters and reclamation plants, coal preparation plants, etc. I tried to tone down my language. Hate could have been "despise", and ugly could have been "horrendous". No emotional involvement here.
RE: HSS10x10 Column Dents
The thing with experience, though, is that it actually has to be relevant in a statistical sense. Was it:
1) 30 years of using sexy concrete encasement details and having no problems OR;
2) 30 years of using horrendous details like mine and having lots of problems?
Only #2 would be statistically meaningful.
I've got this one residential contractor that I work with who had one 4" garage slab on grade settle and crack on him back in the 90's. As far as I can tell, nobody knows just why. For the subsequent 80+ projects, he's forced all of his structural consultants to place one lone screw pile in the middle of all his garage slabs on grade. No thickenings, no grade beams, still 4" SOG. There aren't even studs on the screw piles.
I tried to talk him out of this practice recently on the basis that, in punching shear, the screw pile probably couldn't carry a twentieth of the slab on grade tributary weight for some of these larger garages. He just won't have it. "Experience" has taught him, with absolute certainty, that placing a 4" diameter screw pile in the center of a three car, 4" SOG garage is the silver bullet for avoiding settlement problems. Sub-grade prep and the like are just esoteric concerns.
Experience with what works and experience with what doesn't aren't always the same thing.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents
All I could think of on my own that would work was a concrete encasement detail, but they specifically asked for a steel one as well. I was telling them I didn't think that a steel one would work without being a major operation. KookK's idea changed that, and for that I say thanks KookK!
@hokie, I'm extending benefit of the doubt that you're doing some friendly trolling to stir the pot. If not, I value your input, but I won't always agree with it, and for me that's ok. Fact is, I've never found an engineer I always agree with, and that's a good thing. At first I didn't like KookKs detail for this application because I didn't think it would work. Then I started drawing it and i realized it would work, and work very well.
Lastly, beauty is in the eye of the beholder, and my client wanted a cost effective solution option. So is it the best detail ever? No, but does it work and keep cost down? You bet, which is why my client likes it.
RE: HSS10x10 Column Dents
KootK, I'll hold my tongue.
RE: HSS10x10 Column Dents
!@$#$%^!! You're getting too good at handling me. Might be time for a handle change.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: HSS10x10 Column Dents