ACI SP-309

Abstract

Scope: Preface The need for structural integrity has been recognized ever since the 1968 failure of the Ronan Point Apartment building. Improvements to the ACI code in 1989 required additional reinforcement for structural integrity, however those requirements were based on generally good building practices with little research or analysis to support them. However, since the disproportionate failure of the Murrah Federal building in Oklahoma City, these requirements have received renewed interest and new research conducted. More recently, and primarily due to the aftermath of natural and manmade disasters, the need for designing buildings that are resilient against various hazards has been recognized. While most of the latest research does not directly analyze the efficacy of the structural integrity requirements, it does consider the overall collapse resistance and robustness of reinforced concrete buildings. Research using field experiments conducted in the last decade indicates that reinforced concrete structures are generally robust against local damage like single column removal. Although structural integrity requirements have been included in ACI 318 since 1989, there still exists areas of improvement. For example, recent laboratory experiments show that flat plate structures may still be vulnerable due to the high likelihood of progressive punching shear failures. Furthermore, for structures designed and built without structural integrity provisions, new research highlights ways to improve their robustness and collapse resistance. Finally, improved analysis models and predictions on the likelihood of collapse lead to better assessment of the risks of collapse. ACI Committee 377 sponsored two sessions during the Fall 2014 ACI convention in Washington, DC to highlight the importance of structural integrity and resilience of reinforced concrete and precast/prestressed structures subjected to extreme loading conditions. The sessions sought papers on topics including improving the structural integrity of structures, minimum level of required integrity, integrity of precast/prestressed structures, performance-based structural integrity and resilience, infrastructure resilience, issues and new developments in modeling, and assessment of existing structures. Both experimental and analytical investigations were presented. The sessions presented 10 papers covering the design of reinforced concrete buildings against progressive collapse, evaluation of NYC code provisions, analysis and experimental testing of post-tensioned and precast/prestressed structures, methods to improve collapse resistance, and probabilistic analysis of collapse. This special publication includes eight papers that were presented during the sessions. The papers are alphabetically ordered based on the last names of the first authors.