Concrete-filled thin-walled steel SHS and RHS beam-columns subjected to cyclic loading

Abstract

The flexural force-deformation behavior of concrete-filled thin-walled steel SHS and RHS beam-columns was experimentally investigated and the results presented in this paper. The parameters in the study included the depth-to-width ratio (β), the core concrete strength ( f cu), and the axial load level ( n). Thirty concrete-filled thin-walled steel SHS and RHS beam-column specimens were tested under constant axial load and cyclically increasing flexural loading. A mechanics model is developed in this paper for concrete-filled steel SHS and RHS columns subjected to constant axial load and cyclically increasing flexural loading, and is a development of the analysis used for monotonically loading condition (Han et al., 2001) [1]. The predicted cyclic responses for the composite columns are in good agreement with test results. Based on the theoretical model, parametric analysis was performed on the behaviors of moment ( M) versus curvature ( φ) response, lateral load ( P) versus lateral displacement (Δ) relationship, as well as ductility coefficient (μ) for the composite beam-columns. Finally, simplified models for the moment ( M) versus curvature ( φ) response, and the lateral load ( P) versus lateral displacement (Δ) relationship were suggested. Formula should be suitable for incorporation into building code, for the calculation of the ductility coefficient (μ) of the composite beam-columns under constant axial load and cyclically increasing flexural loading was developed.