Steel wire or iron wire. spool of wire used mainly in the iron frame of the building foundation..
Steel wire is used to brace beams and columns as well as to reinforce concrete (rods are also used to reinforce concrete). This is because steel wire has a high tensile strength and is flexible. These two properties make steel wire suitable for suspension bridges and for winding elevators (lifts).
Steel wires have high strength than the usual reinforcement bars and usually it is used for prestress or post tension beams which can span very big spans without mid supports, especially good for bridges railways bridges and flyovers.
What burns in a building are mostly the furnishings and interior, not the frame it's made of. Steel buildings are more expensive to insure against fire than wood frame buildings, because in a fire more steel is damaged by warping and distortion than would happen in a wood-framed structure, and wood structures are easier (and cheaper) to repair. Of course, if everything in a building was non-flammable, fire would never occur. That doesn't usually happen, though, and it's all the flammable stuff that most buildings house inside that burns.
