NONLINEAR DYNAMIC PROGRESSIVE COLLAPSE ANALYSIS OF COMPOSITE FRAMES WITH CONCRETE-FILLED STEEL TUBULAR COLUMNS BASED ON FIBER MODEL

This paper established a finite element (FE) model of spatial composite frame with concrete-filled steel tubular (CFST) columns based on nonlinear fiber beam-column element theory, and then investigated its anti-progressive collapse behavior subjected to abnormal loadings such as fire, blast or shock. The user-defined material models of concrete and steel were incorporated in subprogram UMAT provided by ABAQUS software. The user-defined material models were verified by reported experimental results. Nonlinear dynamic progressive collapse analysis of a typical 12-story spatial composite frame was performed under different initial failure modes. The results show that the internal forces of columns and beams are redistributed due to the failure of column, and the bending moments and axial forces of adjacent components change significantly. The redistribution of internal forces during unloading follows the “shortest path principle” in general. The maximum vertical displacements of upper level joints are associated with the damage of middle columns at the bottom, while the minimum vertical displacements of upper level joints are associated with the damage of corner columns at the bottom. The spatial composite frame with CFST columns has good anti-progressive collapse behavior.