Steel-Concrete Composite Columns

Abstract

Structural steel shapes and tubes can be used with concrete to produce structural components. The performance of such composite systems, is better than the sum of responses of the parts taken separately. In a concrete-filled steel tube caisson, for example, the steel casing resists flexural tension efficiently while confining the concrete core as the core resists axial compression, whereas it also stabilizes the steel casing. Concrete encasement of structural steel shapes can provide lateral stability to the steel shape, restraining local buckling as well as reducing the slenderness ratio below that of the steel shape alone. Concrete encasement serves as insulation for fire and shock loading. Characteristics of the structural behavior of composite columns are described as the basis for design recommendations. Strength design principles from Load and Resistance Factor Design of the American Institute of Steel and Construction and the American Concrete Institute are used in design. Shear transfer for the effective interaction of concrete and steel is considered, and requirements for transverse bar reinforcement of shear mechanisms are discussed. Design examples of strength estimates for two types of composite columns are included.