A CYCLIC NONLINEAR MODEL FOR CONCRETE-FILLED TUBES .2. VERIFICATION

Part I of this two-part paper presents a three-dimensional (3D) cyclic nonlinear finite-element macromodel for concrete-filled steel tube (C FT) beam-columns and composite frame structures. The material formulat ion consists of a concentrated plasticity bounding surface model in 3D stress-resultant (force) space. Part II presents the calibration of t he 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 it s accuracy for a wide range of CFT cross-section sizes and material st rengths. A final study compares this CFT finite element to an experime nt consisting of a cyclically loaded 3D subassemblage composed of stee l I-girders framing rigidly from three sides into a CFT beam-column. T his CFT beam finite element is suitable for conducting monotonic stati c, cyclic static, or transient dynamic analysis of complete composite CFT unbraced frame structures, for executing seismic ''push-over'' ana lyses of composite CFT structures, and for conducting advanced inelast ic analyses of composite CFT frames directly for design.