Dent in structural Column

[Rinku12]

Hello Experts,

A dent was observed during the erection of one the column. The dent is very local and at its worst spot it is 4mm concaved by 3” x3” overall in a height of 15 inch. There is less than 1mm of deflection in the area just above 3” x 3” square as shown in the pictures and hence the damage is very local.

The column is part of monorail support structure which will be used once in 5 years. The column is HSS 305 X 305X 9.5 and is 6000mm in length, Root cause of damage is UNKNOWN and the dent was clearly before paint as there is no damage to painting in the effected area.

I am ( AS an EOR) proposing to put steel plates and clamp them to the wall of the HSS TUBE using HOLLO BOLTS to stiffen the section.

As per FABRICATOR:-

1) We suspect the slight deformity originated at the mill during production. The allowable concavity of the HSS is defined by Steel Tube Institute (STI) publication ‘22840_Tolerance-Brochure_10820’. This allows for a convexity or concavity of 0.01x the flat wall dimension. In our case that would be approx. 2mm to 3mm. Please note that using a measuring tape or caliper is not an accepted method for measurement, precision calipers should be used.
2) It appears that one measurement may be slightly out of tolerance. We suggest the EOR review the column and determine if the column as provided is acceptable. Our suspicion is that the column will be found to be adequate in the ‘as is’ condition.

I would appreciate you advise on this beause as per AISC even defects in unidentified steel is not permitted so i think we need to repair this even if its slighlty out of tolerance. I will share the detail later once done once i hear from you experts

 

[JoshPlumSE]

What's the worst case loading for this column (axial & bending) vs the capacity of the column (axial and bending)?

Unless the column is stressed to 99.9% of capacity, I'd be surprised if this were signficant enough to reject it..... Now, if this were the case for ALL columns on the job, then you could make a pretty good argument that the steel fabricator isn't supplying the steel properly.

Any other issues with the column? Is the cross section warped or deformed in any other way? Is the overall straightness of the column compromised?

 

[dik]

Can you just weld a BAR 1/4x2-1/2 over the point of impact? Likely less costly than Hollo Bolts... check to see if column strength is greatly impared?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[WARose]

I've checked minor dings in columns before and it wasn't a issue. Usually the global buckling issue is big before the local one. (That can change if the column has slender/noncompact elements.)

 

[MIStructE_IRE]

I don’t have an answer for you - but i HATE when someone else tries to put me in a position to accept something like this through no fault of my own! At the end of the day its your name and your insurance on the line. You’re being asked to just accept this, while not being able to put any great science behind it, because someone else fcuked up! Very annoying.

 

[ATSE]

Considering the many tolerances for steel and concrete in building construction, it seems a bit extreme to reject or even retrofit this column based on this relatively minor defect shown.
A construction site is not a surgery center - members either arrive damaged or get damaged during erection on most projects. Yes, the Contractor ultimately takes responsibility, but I believe a good engineer doesn't grandstand or make a mountain out of a mole hill.
As noted above, if your demand / capacity ratio is low, let it go; make the Contractor sweat for a couple of days, make sure everyone knows you worked the weekend to solve the challenging problem, then give the owner the good news.

 

[bugbus]

Agree with JoshPlumSE, if the utilisation is near 100% I would look into it in a bit more detail, otherwise I can't see it being a problem.

Columns like this get dented all the time in service without much problem.

 

[SlideRuleEra]

A dent was observed during the erection of one the column.
I am ( AS an EOR) proposing...

Discuss the situation with the Owner before making any decision. The Owner may have plans for the use of structure (of which you know nothing) that make the problem either "unacceptable" or "trivial". Based on that input, make your recommendation to the Owner. I agree the most likely course of action is to accept column and leave it "as-is".

There is always the additional option to accept the column and negotiate (in good faith) with the Contractor for a financial credit to the Owner for accepting questionable material... we used that approach frequently on our electric generating station projects.

http://www.SlideRuleEra.net

 

[human909]

As others have mentioned the section is barely compromised at all. And unless it is located at a point of maximum demand in the column then it is unlikely to affect anything. Any if it was at a point of maximum demand then you really need to be running with slim margins for it to be an issue.

I am ( AS an EOR) proposing to put steel plates and clamp them to the wall of the HSS TUBE using HOLLO BOLTS to stiffen the section.

Your bolt holes will likely have a bigger effect on the member capacity than that dent. So you'll likely need alot of them and alot of plate for you to end up ahead.

 

[Rinku12]

First of all thanks to all for the valuable comments. I am replying as under

@JoshPlumSE: My D/C =0.82, the external lateral loads acting on the column are basically dynamic i.e. wind and side thrust from the hoist . the dead load is the self weight of the structure plus the 15MT Hoist moving on it. This column is basically supporting the Monorail system. See attached PDF. Basically if i set all the load factors to unity and impact factor to unity ...then I will have D/C=0.43.Its only one column.The column is straight as an arrow on all sides and only the dent on the flat side is effected the corners are straight with no deflection at all.

@Dik: I want to avoid welding ..it may cause other warping issue and as you can see its all painted...yoy know what i mean....with all the Reponses i got on this forum i am leaning towards leaving the column as it is.

@WA Rose: its non-compact section ...and the structure is supporting only 15MT Hoist and i am not concerned with buckling failure as my axial loads are very low.

@MIStructE_IRE : I hear you....that was my first response/feeling when i got the news from the site.

@ATSE: I agree. Mostly likely i will not ttouch after seeing valuable comments herer.Build some confidence.

@human909: Point noted i did all the checks.

@gusmurr:Thank for the feedback.

Please see the attached PDF. After thoughts and number crunching and reviewing all the valuable comments, I decided not to do anything and leave the column as it is.

. [URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1625637183/tips/Model1_i3agib.pdf[/url]