An Approximate Analytical Formulation for the Rise-Time Effect on Dynamic Structural Response Under Column Loss

Dynamic progressive collapse analysis of building structures is usually conducted under sudden column loss conditions. The time length required for disabling the failed column is defined as the rise time. The rise-time effect on the maximum dynamic response of building frames under column loss is investigated in this study. Based on the work-energy principle, an approximate analytical formulation for the maximum dynamic response is derived considering the rise-time effect. The force- and displacement-based dynamic increase factors (DIFs) of a single degree-of-freedom model and a clamped steel beam are used to assess the accuracy and validity of the proposed formulation. Analysis results indicate that the DIFs decrease with increased rise time. Also, the rise-time effect decreases with increased ductility demand. Practical application of the analytical formulation to regular building frames subjected to column loss is illustrated. Primary factors related to the extent of the rise-time effect on the column-loss response are identified for design consideration.