Fiber beam model for fire response simulation of axially loaded concrete filled tubular columns

This paper presents a fiber beam model for the fire response simulation of concrete filled tubular columns of circular section under concentric axial load. The model consists of two parallel components, one with a circular tubular steel section, and the other with a solid circular concrete section. The components interact with nonlinear longitudinal and transverse links at the end nodes. The element is formulated on a system without rigid body modes and accounts for large displacement geometry through the co-rotational formulation connected both longitudinally and transversely at their nodes by link elements. The model is capable of representing different types of concrete infill of the steel tubes: plain, reinforced and steel fiber reinforced concrete of normal or high strength. It is validated against experimental data from column specimens under fire. The results are also compared against a three-dimensional finite element model characterized by its accuracy of fire response simulation.