Cyclic performance of concrete-filled steel CHS columns under flexural loading

Concrete-filled steel CHS (circular hollow section) columns are currently being increasingly used in the construction of buildings. Limited information is available on the models for the moment (M) versus curvature (phi) response, and the lateral load (P) versus lateral displacement (Delta) relationship of these columns subjected to axial load and cyclically increasing flexural loading. Eight concrete-filled steel CHS specimens were tested under constant axial load and cyclically increasing flexural loading. The parameters in the study included the concrete strength (f(cu)) and the axial load level (n). A mechanics model is developed in this paper for concrete-filled steel CHS columns subjected to constant axial load and cyclically increasing flexural loading. The predicted cyclic responses for the composite columns are in pod agreement with test results. Based on the theoretical model, parametric analysis was performed on the behaviours of the moment (M) versus curvature (phi) response, and the lateral load (P) versus lateral displacement (Delta) relationship, as well as the ductility coefficient (mu) for the composite columns. Finally simplified models for the moment (M) versus curvature (phi) response, and the lateral load (P) versus lateral displacement (Delta) relationship are suggested. A formula for the calculation of the ductility coefficient (mu) of the composite columns under constant axial load and cyclically increasing flexural loading is developed. (C) 2004 Elsevier Ltd. All rights reserved.