Macro joint model for progressive collapse analysis of L-shaped CFST column frames

Abstract

In this study, a macro joint model was developed to evaluate the progressive collapse resistance of L-shaped columns composed of concrete-filled steel tube (L-CFST) frames, accounting for joint performance. The methods used to calculate the spring stiffness in each part of the macro joint model were derived using the component method and the deformation coordination principle. Additionally, an L-CFST frame model consisting of fibre beam elements and macro joint models was created. For frame models with different parameters, the dynamic response under column removal was analysed; these parameters included the loading condition, connection type, the location of failed columns, the height and number of floors and the span–depth ratio of the steel beams. The macro joint model was found to have high accuracy in predicting progressive collapse resistance. The L-CFST column frames with novel side-plate reinforced connections fully exploited the catenary mechanism and Vierendeel action. All the variables affected the vertical displacement at the position of the failed columns, with the span–depth ratio having the most significant impact.