Understanding Functionality and Operability for Infrastructure System Resilience

AbstractInfrastructure includes building and lifeline systems essential to supporting community resilience through functionality and operability. A hazard attack (e.g., earthquake or hurricane) can damage systems and abruptly drop their functionality and operability. Operability is a measure of the infrastructure system’s support for community resilience through the ability to adapt and transform to restore basic services for users (an operational level allowing social institutions to provide services), which can be achieved before all system repairs are made. Functionality is a measure of the infrastructure system’s resilience and is not fully restored until all system repairs are completed and operational restrictions removed. Currently, the literature describes both measures as “functionality,” but the dual application of the same term causes confusion and miscommunication. As a result, “operability” is proposed as an important expression also needed to properly measure infrastructure resilience. Full operability is achieved at a functional level when all basic services are restored. This technical note offers practical definitions for functionality and operability within a resilience context and identifies basic service categories to use when analyzing infrastructure system resilience.