Analytical Investigation of Progressive Collapse Resistance Mechanism in Steel Moment Frame with Fiber Model

In order to investigate the resistance mechanism of steel frame structure in progressive collapse, an advanced finite element model(FEM) is presented based on fiber beam-column element. Using this FEM, non-linear static pushdown analysis of a ten-story structure was carried out by the alternate load path method, in the two cases that two different columns are removed respectively. Analytical results show that residual structure has the different resistance mechanism for the different column removal case. In the initial stage, bending resistance mechanism can provide dominate resistance capacity in the structural progressive collapse, after both middle and side columns are removed. However, when the bending resistance is out of work, the catenary action is induced in the case of the middle column removal only, which is not developed after the side column is removed. It can be seen that steel frame structure has higher collapse risk in the case of the side column removal than in the case of the middle column removal.