scope:

The report seeks to summarize our present understanding of collapse initiations, collapse-resisting mechanisms, collapse-resisting strengths of floor systems, and to discuss the role of current integrity provisions in providing resistance to collapse.

This report is designed to be used by engineers, practitioners, and researchers. It will be used to improve understanding of how concrete floor systems redistribute gravity loads following the onset of initial failure. This report can also be used by educators to describe the mechanics of collapse resistance and direct them to the applicable code provisions currently in place.

Each chapter details possible causes of collapse initiation, collapse-resisting mechanisms, collapse-resisting strengths of floor systems, and discussion of relevant code requirements. Chapters 3 and 4 mainly correspond to cast-in-place concrete structures without and with beams, respectively. The focus of Chapter 5 is on precast concrete structures. The report also presents relevant integrity provisions in ACI 318, and CSA A23.3, and the New York City Building Code (2014).

If an engineer is required to perform a comprehensive progressive collapse analysis, including the determination of collapse initiation scenarios, the design guidelines provided by the General Services Administration (GSA) or the Department of Defense (DoD) should be used. Furthermore, this report can be used to supplement current materialspecific GSA and DoD guidelines with the approval of the authority having the jurisdiction over the project.

This report is developed based on analytical and experimental studies conducted on RC elements and structures with uniaxial concrete compressive design strength of approximately 3 to 8 ksi (21 to 55 MPa). Application of the collapse-resisting mechanisms discussed herein to high-strength concrete or high-strength reinforcement requires further study.