NONLINEAR ANALYSIS OF MULTI-CELL T-SHAPED CONCRETE-FILLED STEEL TUBULAR STUB COLUMNS

The confinement that the concrete core is subjected to in multi-cell T-shaped concrete-filled steel tubular (MT-CFST) columns is characterized by defining the equivalent square section and the angle of boundary between effectively confined area and ineffectively confined area of the concrete core. According to experimental results, the constitutive relationship of the concrete core is suggested by means of modifying the expressions of effective lateral pressure and the descending stage in Mander's confined concrete model. Numerical simulation of 8 MT-CFST stub columns under axial load is accomplished based on ABAQUS. The comparisons between calculated results and experimental data demonstrate that the suggested concrete constitutive relationship is applicable for the finite element analysis of MT-CFST columns. Subsequent discussion on the cooperative properties of two materials shows the similarity on mechanism between the MT-CFST columns and other types of CFST columns. Considering the MT-CFST columns as a combination of three rectangular concrete-filled steel tubular units with two extra steel plates removed, the formula for their bearing capacities is proposed based on superposition principle, which may provide some references for engineering practice.