Design of concrete-filled hollow structural steel columns for fire endurance

The benefits of steel hollow structural sections (HSS) from an aesthetic an d structural point of view have long been recognized by architects and engi neers in Canada, and more recently in the United States. However, when buil ding codes require structural fire protection, the cost of providing such p rotection can be expensive for exposed members. Filling an HSS column with concrete not only improves the capacity of the member through composite act ion at ambient temperatures but also provides fire endurance periods of up to 3 hours depending on the load level, section size, concrete strength and reinforcing characteristics. Physical tests and parametric studies recentl y completed at the National Fire Laboratory in Ottawa have resulted in desi gn equations which predict the load carrying capacity and fire endurance pe riod of concentrically loaded HSS columns filled with plain concrete, bar-r einforced concrete and steel fiber-reinforced concrete. The design method i s presented, case studies are used to illustrate potential applications, an d practical suggestions are made regarding construction techniques.