Advanced analysis and design of structures composed of concrete-filled hollow sections

Structures composed of concrete-filled steel hollow sections are widely used to-date due to their structural efficiency and economy. This paper proposes a second-order design method which requires only section capacity check without need of assuming an effective length and using prescriptive formulae in different codes and the shape of the member cross section can be arbitrary. The member-based design by the linear analysis and the effective length assumption is abandoned and replaced by the second-order analysis utilizing an incremental-iterative nonlinear process. Using a curved element allowing for member P-d effects and initial imperfections, the non-linear response of individual members and a frame can be captured directly and used for structure resistance checks. The proposed method could be used for generation of failure surfaces of the arbitrary shaped cross sections and the stress distribution along the concrete component is considered by segments with the entire structural steel section meshed into small fibres for determination of section capacity. Verification of the proposed analysis method is carried out by comparison against examples. It is believed that the proposed approach will be the next-generation design method for modern structures made of members of concrete filled sections of any shape and the new design method is also being implemented in design of composite structures in the consultant firm of the last author.