A Cyclic Nonlinear Model for Concrete-Filled Tubes. II: Verification

Abstract

Part I of this two-part paper presents a three-dimensional (3D) cyclic nonlinear finite-element macromodel for concrete-filled steel tube (CFT) beam-columns and composite frame structures. The material formulation consists of a concentrated plasticity bounding surface model in 3D stress-resultant (force) space. Part II presents the calibration of the material model parameters based on comparison to both monotonic and cyclic experimental results of CFT beam-columns subjected to uniaxial and biaxial bending plus axial force. The macromodel is then verified against a comprehensive set of monotonic experiments, establishing its accuracy for a wide range of CFT cross-section sizes and material strengths. A final study compares this CFT finite element to an experiment consisting of a cyclically loaded 3D subassemblage composed of steel I-girders framing rigidly from three sides into a CFT beam-column. This CFT beam finite element is suitable for conducting monotonic static, cyclic static, or transient dynamic analysis of complete composite CFT unbraced frame structures, for executing seismic “push-over” analyses of composite CFT structures, and for conducting advanced inelastic analyses of composite CFT frames directly for design.