Crack in Bridge Crane Runway Support Beam

Fatigue is a reasonable guess. How often the crane is used (loading cycles) will tell you if fatigue is likely. If it is fatigue, then look at the restraint conditions around the crack. The beam is restrained in some manner then you could get local stress risers.

Got any more photos to put it into context, like size?

Also picture underneath? / bottom face from what you've provided

Is this the vertical face or??

What part of the crane is creating that mark?

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I will be making a site visit to do a thorough inspection in early September.

The photo shows the bottom flange and the web.

DaveAtkins

Ah, now I get it - I though I was looking at a solid beam, but this is flanged web beam?

Does the crack extend all the way on the other web?

There's a curiously similar crack just to the right of the main one?
Equally curios grey metal fragments at the base
Are they through cracks or surface ones?
I wouldn't call that a diagonal crack but just a crack that is propagating based on the load path which isn't purely vertical by the look of it.

Either way I hope it's still not in use...

Age, actual loads, usage, type of steel wheel and any torsional or bending effects need to be considered.

How have they "repaired" it?

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DaveAtkins:
For the moment, you should not be using that crane girder or the crane in that area of the bldg. The crane may well influence the stresses in that particular crane girder when it is in adjacent spans of that crane rail line. Have someone drill .5” dia. holes at the tips of the two cracks, with the crack tip as the center of the drilled hole. Clean up the rough edges of the drilled holes, so as not to leave sharp edges and new stress raisers. That’s one hole in the web at big crack tip, and another hole in the flg. at the shorter flg. crack tip. These will tend to arrest the crack growth, although neither of the cracks look very new. The upper part of the web crack could be fairly new, and you should be able to see that. The drilled hole changes the crack tip from an infinitely small crack tip radius (and infinite crack tip stress), to a radius of some finite radius, and a lesser max. stress. And, from the crack propagation standpoint this starts to reduce the chance that the crack will continue to grow unabated. Find a Fracture Mechanics textbook or a real good Strength of Materials or a Theory of Elasticity textbook, and do a little self-study. Then, get out there and investigate for stress raisers, and stress conditions which might have caused this. Look at connections in the immediate area, beam continuity, stress reversals, crane operating history and max. loads lifted near that girder line, etc. Question the client on their crane and crane rail system inspection procedures, and crane operation procedures etc., to start to hone in on the cause of the problem.

There is a lot of corrosion there. The ragged look of the bottom flange is unusual, and it does appear that other cracks may be initiating in that area. What processes take place in the building?

Checking the original thickness vs now might be a good start.

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Provide more info.. there is only one picture and some explanation.. This will be speculation but my first assumptions are ,

i= The crane runway support beam is not hot rolled but steel girder fabricated from plates . I suspect the brittle crack is due to stress concentration , residual welding stresses . will you try to learn the manufacturing process of the beam, ambient temperature of the working environment ?

ii= the crane runway support beams should normally be simply supported .. your statement implies , the crack(s) developed at around 1/4 L. Provide more info . for the support conds, beam size,web and flange thk. crane properties ..to get better responds