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 Originally Posted by JKDS
Can jet fuel melt steel beams? I'm asking for a friend...
Well, we had a good run, boys. The last 3.5 years was fun, right? Anyway, gotta run.
OK, bye.
Seriously, though.
Steel comes in many grades, which have different material properties. It's hard to find specific information about the melting point of various steels, but online searches get me in the ballpark of 1,500 C.
Jet fuels burn at a wide range of temperatures, depending on the specific application and fuel.
I'll talk about the most common jet fuels Jet A and Jet A-1. Jet B burns at a lower temp.
I found an odd bit of information about jet fuels called the "max adiabatic burn temp" on wikipedia, which attributes a value of ~4,000 F (~2,200 C).
Adiabatic means (roughly) a process which does not transfer thermal energy. I like to think this means whatever we're talking about is happening in a perfectly thermally insulated container.
I assume that the max adiabatic burn temp is talking about the temperature of the flames at the center of the flames, roughly.
Steel melts at ~2,800 F (~1,500 C).
Jet A burns at ~1,900 F (~1,000 C).
max adiabatic burn tem of Jet A: ~4,000 F (~2,200 C)
It's hard to tell on the face of it how close an approximation this would be for, say, a concrete walled elevator shaft whose walls are coated with burning fuel. (Just to grab a totally random, but presumably common test situation.) If there is a lot of exposed surface area of fuel, then the rate of burning will be high and the temp will be high. If the fuel has low surface area or the ventilation is too low, then the fire will be cooler or maybe even choke itself out due to lack of Oxygen.
I'd say that it is plausible that jet fuel can melt steel, given the right conditions.
It's important to note that steel loses it's structural integrity at a rapid rate when it's temperature rises to and increases past ~1,500 F. However, it's also important to note that architectural structures are typically built with a Factor of Safety at ~50+. A typical guess would be that the structural steel in a building would need to be reduced to (at most) 2% of it's nominal strength to fail. Another competing factor is the type of loading. If a structural element is meant to only be in compression, and it is subjected to a bending load, then there will be both compression and tension in the element, which can drive it's nominal failure conditions.
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EDIT
At the WTCs on 9/11, jet fuel wasn't the only thing burning. The jet fuel was the catalyst for the WTC fires, but the resulting inferno was intensified by the combustible material inside the buildings. The fuel was the ignition source, which burned for maybe 10 minutes.
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