Remedy for flame-cutting of steel beam

[Amesofe]

In my abscence, an equipment installer decided to flame-cut an 18 inch notch in the compression flange of W 10 steel beam at mid-span, including two (2) inches of the web. I am reluctant to strengthen the beam in the notched area by welding or bolting stiffeners or replacing the lost flange. The embrittlement of the steel in the notched area is of great concern and I lean toward a replacement of the beam. What is the extent of heat damaged area or embrittlement caused by flame cutting of structural steel?

 

[ishvaaag]

If your thing undergoes fatigue even low cycle, replace the thing. You name fatigue so go for it. The only consideration is whether the necessary substitution won't produce also necessary negative fatigue or fragility effects as derived from the possible reconstruction process.

If no vibration and non seismic, maybe any safe reinforcement scheme be valid.

HAZ extension for flame cut one site says be similar to welds. For aluminum welds 25 mm is suggested whilst being said be bigger relatively than in steel...except yo find better, think of 25 mm as well, on account of shapes being bigger.

 

[JAE]

Agree with the second paragraph of ishvaaag above. If your flange is in compression always, there is no fear of fatigue so the embrittlement isn't as big an issue. Adding additional steel plating, larger than the original flange, and welding such that the connection is higher than the ultimate capacity of the top flange cross section is a possible alternative.

The other, is to slap the equipment installer's hands, chain his wrists, and hang him from the beam for 24 hours to load test the beam. With the load test completed, conclude that the beam must be replaced due to some technical concept way beyond his understanding... i.e. the beam is broke!!

 

[Ron]

Agree completely with JAE...particularly last paragraph, with one exception...be specific about the particular anatomical parts by which he will hang.

 

[JAE]

Well, I didn't want to get red-flagged.

 

[DaveVikingPE]

This is really interesting - the HAZ part, not the tortures (though appropriate they are). Has anyone done any modelling of flame cut steel beams/with the accompanying visuals one could view on the web? Also, how was the 25 mm figure determined? I don't have a lot of experience other than the basics of what the heat-affected zone is, is there a "standard" or at least recognized formula for determining this? I'd assume it's based on time after cutting, etc.

 

[ishvaaag]

OK since I placed it I will say what I did. I searched the web, and since I found what posted in 5 minutes I bet more is surely to be found. 1st finding was that for flame cut plus HAZ the information was not coming. Second was statement of HAZ zones being of similar extent for flame cuts than for welds. The weld plus HAZ search was more fruitful and in aluminum soon gave 25 mm "be the HAZ zone". (They must have some specifical objects in aluminum in mind...or unknown size fo me ..windows shapes, skylight, aerospace?). It also noted more or less "relatively bigger than in steel due to the higher heat conductivity of aluminum". Then I dared to think the shapes in aluminum (and heat input) be lesser, and hence on the bigger shapes of steel and higher heat input but less conductivity of steel I ventured -that no derived- the HAZ be in the same 25 mm range. I assume that searching the web you can find far more accurate statements of the HAZ extent and shape. For giant welds, somewhat bigger HAZ zones must be expected, but in any case proportional to the sizes I don't expect them be, melting simply must prevent that and circumscribe it to some depth comensurate to the electrode deposition (er, I don't think in sinterization ways yet). I used Google as search engine.

And, if you find something, it would be interesting to ascertaing how accurate one can be guessing.