Sometimes what isn’t visible at a crime scene is just as important as what is.
***UPDATE*** note the updated truss count. My original estimate of 23,000 trusses was based on the idea that they used single trusses in between the section breaks when in fact they did not, they used double trusses everywhere on each floor. My first count was based on doing a layout of the truss structure and then simply counting and multiplying that number by the number of floors which used these trusses. Turns out, the number of missing trusses is actually double my original number… about 43,000 – 46,000. With that one exception, I believe the research in this article still stands.
Carbon steels which can successfully undergo heat-treatment have a carbon content in the range of 0.30–1.70% by weight. Trace impurities of various other elements can have a significant effect on the quality of the resulting steel. Trace amounts of sulfur in particular make the steel red-short. Low alloy carbon steel, such as A36 grade, contains about 0.05% sulfur and melts around 1426–1538 °C (2600–2800 °F). Wiki