Crack on Steel Beam??? 1

[KimWT]

Hi!

We have been using W24x131 to lift precast concrete products in the yard.
Recently we found a line (crack?) only underside surface of bottom flange.
But, when we checked the top surface of bottom flange, we could not find any crack or line.

What is this line (crack)?
What caused this one?
Could it be related with fatigue failure? (This has been used more than 20 years.)

Thanks for your time!

 

[TehMightyEngineer]

I'm gonna go with local flange bending combined with beam flexure causing a fatigue failure. Very unusual crack location though; would have expected that on the top face of the flange not the bottom face.

Either way, scrap the beam and get a new beam fabricated. Make sure it's designed per ASME BTH-1-2017.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[TehMightyEngineer]

I'd also guess that if you cut the flange perpendicular to the crack that you'll find it originated inside the root of the flange/web joint. Looking at the failure surface will definitely tell you what the failure mode was.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[KimWT]

This happened only at one end...

 

[Ron]

This looks more like a rolling anomaly than a fatigue crack. It probably opened up from repetitive loading, but looks more like a cold shut.

 

[TehMightyEngineer]

Oh good point Ron, I hadn't thought of rolling anomaly. Either way I'd cut out a sample of the crack to confirm exactly the cause of failure and it might be worth sampling some uncracked areas. I'd definitely scrap the beam rather than try to repair it.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[SAIL3]

I would go with the rolling anomaly also...unusual location and relatively straight....

 

[FLCraneBuilder]

looks more like a rolling scar to me - but obviously hard to tell from pics
grind n a bit & check depth?

 

[KimWT]

Thanks for replies!

Rolling anomaly...
So, is this looking like s problem in production process?
Is this relatively not rare in the steel industry?

 

[TehMightyEngineer]

Yeah, I'd agree that a production issue is more likely than my theory; but you really wont know until you cut a cross-section of the crack to see how it propagated and how the steel looks inside the flange.

My understanding is a rolling issue isn't that rare but it is rare for it to leave the yard with a major defect. I imagine this defect was embedded in the flange to web joint and thus wasn't picked up visually and a defect detection system likely would have difficulty finding it as well.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/