Analytical Load and Dynamic Increase Factors for Progressive Collapse Analysis of Building Frames

Proposed analytical expressions for the load increase factor (LIF) and dynamic increase factor (DIF) are compared with the empirical formulae recommended in the Unified Facilities Criteria (UFC) guidelines UFC 4-023-03 in this study. Static and incremental dynamic analyses are carried out for two moment-resisting frames under sudden column loss. The LIF and DIF of the column-removed frames are estimated from their load-displacement envelopes. They are used to evaluate the adequacy of the analytical LIF and DIF expressions in comparison with the empirical formulae. The study results indicate that the proposed analytical expressions may be an alternative in estimating the LIF and DIF for progressive collapse analysis.