ABSTRACT
Structural systems for multi-storey buildings are usually either steel, reinforced concrete or a combination of the two. Steel columns are less bulky than reinforced concrete columns, but steel is badly affected by extreme heat and so always needs fire protection: steel melts at 1375ºC. A steel foundry will smelt iron ore to create iron by burning off all impurities through blasting the molten metal with oxygen. A small amount of carbon is retained, mixed with the iron and this creates steel. Steel is incredibly strong, dense and heavy – a cubic metre of steel weighs over 7.8 tonnes, so usually only a thin slice of steel is needed. Steel-framed buildings can also use steel Circular Hollow Sections for columns: a little more expensive than a Universal Column, but they achieve a great appearance when left exposed internally. Steel beams – often still called I beams – are tall and thin: proportionally, about a third to a half as wide as they are deep.
