"The photograph illustrates steel beams in an parking garage that are supporting a floor deck where heavy motor vehicles are stored. Due to the building's size, the structural elements must be protected to a minimum one-hour fire resistance rating. In this particular example, the steel's fire resistance rating is achieved through concrete encasement."
Coffee Break Training - Fire Protection Series No. FP-2006-19
United States Fire Administration: http://www.usfa.fema.gov/