Assessment of design requirements against progressive collapse in UFC 4-023-03: Numerical simulation

Unified Facilities Criteria (UFC 4-023-03): Design of Buildings to Resist Progressive Collapse published by the Department of Defense is one of the few design provisions that have been used around the US which provide design requirements on the basis of conventional design philosophy to the designers and the owners of the buildings against progressive collapse. These requirements are evaluated using numerical models which have been shown to be able to reasonably capture the behaviors of the buildings under column loss scenarios. A large number of case studies are conducted using validated three-dimensional macro-based models for four prototype buildings with different size, different height, different seismic detailing and different structural layouts. The simulation results show that the tie force method (TFM) is effective in protecting steel framed buildings against progressive collapse and can significantly reduce overall deformations of the structures after sudden loss of a column. However, the method for calculating the dynamic increase factor (DIF) proposed in the document is deemed problematic and thus a new energy-based approach is proposed to assess the peak dynamic displacement (PDD). The proposed method is shown to be accurate and reasonably conservative.