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

Abstract

Linear and nonlinear static procedures for evaluating the alternative load paths of building frames under column loss conditions have been refined in the latest Unified Facilities Criteria UFC 4-023-03 in 2009. One substantial modification in the 2009 version is the consideration of material nonlinearity for the load increase factor (LIF) and dynamic increase factor (DIF) in static analyses. In this study, analytical LIF and DIF expressions are compared with the empirical formulae recommended in the UFC guidelines. Static and dynamic analyses are carried out for eight moment-resisting frames subjected to column loss. The resulting LIFs and DIFs are used to evaluate the adequacy of the analytical expressions as compared to the empirical formulae. Accuracy of the analytical formulae in predicting the collapse resistance is also demonstrated. The study results indicate that the proposed analytical expressions may be an alternative in estimating the LIF and DIF for progressive collapse analysis.