Risk Assessment to Support Design to Resist Disproportionate Collapse

The ASCE SEI Committee on Progressive Collapse Standards and Guidance is developing a guidance document to address collapse resistance in buildings. The document will provide a variety of approaches for design to resist disproportionate collapse. In addition to providing design approaches, the document will also include guidance for owners, architects, and engineers on how to use risk assessment to determine the likely loads on the building and the recommended design approaches to reduce the potential for disproportionate collapse. Risk assessment provides a rational basis for decision-making related to design against disproportionate collapse, particularly when there is currently no consensus as to when such design is needed and to what level of resistance. The risk assessment informs the design process by focusing on: defining the desired performance level, identifying the hazards (including likelihood of occurrence and corresponding loads), and ultimately determining the specific design criteria that will — for the likely loads — achieve the desired performance. This process has been developed and vetted in recent years for specific hazards (e.g., seismic design), but has not been fully developed for collapse prevention for buildings subjected to multiple hazards, particularly intentional hazards. The focus of this paper is on the development of this process, i.e., use of risk assessment for identifying the hazards (as a function of building use, occupancy, location, criticality, size, structural vulnerabilities, architectural features, etc.), the likelihood of hazard occurrence (including the options for hazard avoidance), the anticipated loads, and the recommended design approaches to reduce the potential for disproportionate collapse.