Designing Mass Timber Construction to Mitigate the Potential for Disproportionate Collapse

Since the Ronan Point Apartments incident in 1968, there has been a push to inculcate design and detailing measures into mid and high rise buildings that would mitigate the potential for disproportionate collapse in the wake of an extreme loading event (e.g., explosion). At the present time, UFC 4-023-03 “Design of Buildings to Resist Progressive Collapse“ is used by the Department of Defense, Department of State, and other entities to define design requirements aimed at reducing the potential for disproportionate collapse. Since 2016 (i.e., the year UFC 4-023-03 was last updated), there has been growth in the use of mass timber structural systems in buildings constructed in the United States. As such, an effort was recently completed that updated UFC 4-023-03 specifically for mass timber systems. This presentation describes the updated provisions to UFC 4-023-03. Furthermore, a design example that illustrates the primary strategies that can be utilized to mitigate the potential for disproportionate collapse of mass timber buildings is described in detail. K&C, LERA, and KPFF, who each have experience in designing mass timber structures for progressive collapse resistance, worked closely with the U.S. Army Corps of Engineers Protective Design Center to develop these UFC 4-023-03 updates.