Fire protection, reinforced concrete has its fire protection built in. Steel frame requires fire protection. Historically, concrete was used to surround steel members to give adequate fire protection, but this added to weight, slowed down operations, need more site space, became costly, needed more substantial foundations etc., therefore not so advantageous. Also the use of painted fire protection to steel is very lightweight. Most buildings undergo change throughout their life-span.
Buildings often require extension and alteration.
Steel framed structures are easier to extend than concrete framed structures and so future usage may be a deciding factor. By removing fire protection from steel members, additional steel members can either be bolted or welded to the frame. Extension of concrete frame results in more laborious and costly removal of concrete and knitting of reinforcement to provide the necessary integrity of the new concrete frame members. Steel frame structures are usually built using standard universal beam and column sections with associated hollow, channel, angle and T sections which are all available in mild steel or high tensile steel. Generally, rigid joints are formed by the use of welded joints or a type of friction bolt or torque bolt.