Effects of Axial Force Fluctuations on Seismic Behavior of Steel Box Column

To investigate the influence mechanism of axial force fluctuation on the seismic behaviors of steel box columns, the seismic behaviors of steel box columns under 5 patterns of eccentrically fluctuant axial force were numerically analyzed by finite element simulation. The influence rules of axial force fluctuation on their load-displacement hysteresis loops, skeleton curves, displacement ductility coefficients and energy dissipation capacities were discussed. The research results show that the loading frequency of a fluctuant axial force has an significant effect on the seismic behavior of a steel box column—when the loading frequency increases, the seismic behavior deteriorates rapidly. A large amplitude of the fluctuant axial force results in the severe degeneration of load-bearing capacity of a steel box column. When the width-to-thickness ratio of plates in steel box columns is small, the effects of axial force fluctuation on the seismic behavior become conspicuous. As a result, the adverse effects of axial force fluctuation on the seismic behaviors of the columns should be sufficiently considered when the seismic measures of steel box columns in a large span spatial structure are established.