Best Practices for Reducing the Potential for Progressive Collapse in Buildings (NISTIR 7396)

This document is intended to provide owners and practicing engineers with current “best practices” to reduce the likelihood of progressive collapse of buildings in the event of abnormal loading. The report includes a discussion of an acceptable risk approach to progressive collapse, which involves defining the threat, event control, and structural design to resist postulated event. Practical means for reducing risk for new and existing buildings are presented. An extensive review is provided of the design methods used to enhance a buildings resistance to progressive collapse. These include the indirect method (providing sufficient tie forces), the specific local resistance method (designing key elements to withstand abnormal loads), and the alternate load path method (allowing for redistribution of load in the event of the loss of a key member). Design considerations for different structural materials are summarized. The methodology for evaluating and mitigating progressive collapse potential in existing buildings is also discussed. Three appendices provide supporting information. Appendix A presents a worldwide review of progressive collapse provisions in various national design standards. Appendix B identifies knowledge gaps related to progressive collapse that require research. Appendix C provides case studies of progressive collapses. This document is not intended to provide step-by-step design guidance for practicing engineers