Study on collapse mechanism of steel frame with CFST-columns under column-removal scenario

The design of structure against progressive collapse has tended towards more quantitative design where utilizing catenary action becomes essential. In this paper, a single internal column removal test was conducted for a 1/3 scale 4-bay steel frame with concrete-filled steel tubular (CFST) columns. The anti-collapse mechanism of the frame under the scenario of column loss is discussed. Both FE model and simplified analytical model are developed to investigate the behavior of steel frame with CFST columns in resisting progressive collapse. The accuracy of the two models is verified through the experimental results. The anti-collapse measures of the proposed model are sensitive to the modeling techniques used to simulate the CFST columns. A method based on the energy equivalence is used to evaluate the dynamic behavior of the frame. The results show that the DAF (dynamic amplification factor) value of 2.0 which is recommended by DoD provision in linear static analysis is reasonable. However the mobilization of “catenary action” which is not considered in DoD provision would increase the DAF value as currently given in DoD.