Steel Beam With Crack 1

[Jackcsh]

A new W36x330 bridge beam arrived from the fabricator with a longitudinal crack in the web at the neutral axis. The crack is about 4ft long starting from one end of the beam. Visually, the width of the crack at the surface is maybe 1/16", the depth of the crack is small, about 1/32". Thought grinding the crack, welding, then grinding flush as possible repair solution. Any other suggestions?

 

[bridgebuster]

If there's no structural concernGrind it flush; don't weld it; drill a 7/8" diameter hole at each end, as a precaution; back charge the fabricator.

 

[SlideRuleEra]

Jackcsh - IMHO, don't develop a repair. Instead, contact the fabricator and have them propose a repair for the Engineer's acceptance (notice that I did not say approval). If the Engineer and the Owner agree with the proposal (appearance of the bridge may be important to the Owner), have the fabricator make arrangements to have the repair made (all of this at the fabricator's expense). I'm sure Bridgebuster's solution is sound advice and I have no problem with it, but there is no need for the Engineer to assume any of the responsibility for unintended consequences that may occur.

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[dhengr]

Sounds like it might be a scratch, a tool dragged on the surface during beam movement on a beam line, during fabrication. Is it straight and fairly well shaped or is it ragged and jagged, with sharp terminations in its depth and terminal point? What would cause that shape (width and depth) of surface cracking? That’s not a particularly high residual stress location from rolling and cooling. Is it just a rolling flaw of some sort? Where and why would that kind of surface crack start and stop, it’s not even been loaded yet? Have the fabricator find the cut-off from that beam, or the next beam cut from that string. Is there any cracking in that piece which might indicate a flaw from the mill. Without knowing more I’m inclined to agree with bridgebuster’s fix.

 

[JAE]

Or it could be a fatigue crack from a poor shim layout during transportation of the raw beam stock material or the finished beam.

With a VERY poor layout where the beam would possibly flex about its web with other beams stacked on top.

I'm not sure if there would be enough cycles to cause that but I suppose it depends on the degree of stress that it was under.

How does the repaired crack relate to the final bridge in-place stress exposures? The weld would kick you up to a higher stress condition and possibly alter the final bridge design from a fatigue aspect.

 

[Jackcsh]

Added a photo of the crack. I think having the fabricator respond may shed some light on the cause.

 

[SAIL3]

I would not rush to judgement on this....the jagged nature of this crack is puzzling...can not come up with a viable cause at the moment....I would gather all the info/input from the mill and ,if necessary, consult an expert on mill proceedure(rolling & cooling, etc), then move on to the fabrication process and finally the handling and shipping....if I was the EOR. I would not approve any fix unless I was certain of the cause...we have all been in situations where we have felt the pressure of accepting something we are not comfortable with as the responsible engr...in this case, fortunately, the cost is limited to this one beam...worst case senario..have the fabricator supply new beam..

 

[bridgebuster]

Can you post another photo? What is the vertical edge at the left of the photo?

 

[Jackcsh]

bridgebuster, here is an additional photo

By the way, thanks to everyone for their input.

 

[paddingtongreen]

Is it, according to ASTM A6, an "acceptable blemish"?
If yes, it is not a mill or fabricator problem.
Is it acceptable cosmetically?
If yes, just accept it.
If not, consider what you want done.

If not an acceptable blemish, tell the fabricator and ask what he proposes to do about it, subject to the engineer's acceptance.
Think about NDT, say UT or RT to check the depth and/or the fix if it is in doubt.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[JAE]

That is a very weird crack - if it is a crack. It appears as a crack on the side view of the web - but from the end of the web, it appears that there is some kind of almost lamination on the side that is cracked and the remaining interior of the web is unaffected.

 

[charliealphabravo]

It looks more like a crease that was rolled into the metal during milling. Perhaps there was a temperature control issue.

 

[SlideRuleEra]

JAE's and charliealphabravo's comments reminded me that I have seen something like this before, but on a bigger scale. In the early 1980's we received the structural steel for an electric generating station. Many members, but not all, were covered with what looked like shallow laminations that were tightly bonded to the underlying steel; we referred to it as "alligator steel" at the time. After a few weeks of investigation it was determined that, in this case, it was a cosmetic defect - the steel was accepted and used "as-is".

Did some looking today; according to this link it may be "scabs", it can occur on a small scale and look like the photos Jackcsh posted. See pages 7 and 8.

http://www.cielffa.org/download/ZeroDefectStrategy_download_17-11-09.pdf

I would suggest getting the fabricator to investigate, this is his problem.

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[inline6]

this doesn't look like a crack to me. cracks have sharp edges where as this looks different.

it may even be possible just blend it out by grinding?

 

[Ron]

I was not able to open the photos, but from the descriptions, it sounds more like a rolling defect from the mill. That would make me suspect the entire beam. It should be check for laminations. The depth and orientation of this anomaly can be checked ultrasonically. If there are laminations in the beam, there are likely inclusions as well...not something you want in a fracture critical component.

 

[SAIL3]

agree with Ron...looks like a rolling defect..if this turns out to be true, then, as he said, there may be other defects more serious that are not visible....this would also cause me to take a second look at the fabricator and inspect more closely any other steel that this fabricator has supplied on the project....

 

[Jackcsh]

Thanks to everyone for your input. We are taking a closer look at this defect and gathering additional information. For those interested, I will report back on our findings. And again, thanks for the input; it was very helpful.

 

[dhengr]

Jackcsh:
That’s obviously not a tool mark, now that we see some photos of it. I’ll bet that area was shocked (quenched) in some way during cooling, right after rolling. Hit with much more water, right on that surface and in that area, than the rest of the member, at the end of the rolling process. It certainly is the fabricator’s problem, and probably the mill’s problem. I’d want to see them check the chemistry and hardness in that region of the beam and again some distance removed from that area. I don’t think the vert. dark line right near the web surface (on the right) indicates a lamination, although that would certainly arrest the crack depth at the lamination. I can’t see that from here.

 

[Compositepro]

My guess is that the surface of the beam had cooled too much when it was hot rolled. The hot steel in the center flowed during rolling but the cold skin tore.

 

[charliealphabravo]

I just got two notifications but there is only one new one here...why does that happen??