F-Rec Framework: Novel Framework for Probabilistic Evaluation of Functional Recovery of Building Systems
Authors: Terzic Vesna , Villaneuva Peny , Saldana Daniel , Yoo Dong 
Published: March 2022

Earthquakes are one of the most destructive natural disasters with potentially devastating consequences on communities and the supporting infrastructure. To mitigate the effects of earthquakes on communities and infrastructure, the recovery process of building systems should be considered during the design of the building as it is essential for continued operation. This study presents a novel, probabilistic, building-level framework for modeling and evaluating the entire recovery process (F-Rec Framework), including a building’s post-earthquake functionality along with duration and path of functional recovery. The proposed framework considers all structural and nonstructural building components/systems. It consists of three novel and integrated methods for evaluation building's post-earthquake functionality, mobilization time, and repair time. The framework—in line with the probabilistic performance-based earthquake engineering methodology—uses FEMA P-58 damage/performance assessment results to evaluate the recovery process. With its modular structure, this framework is extendable and lends itself to the additional of new components. The method for evaluating a building’s post-earthquake functionality utilizes FEMA P-58 damage assessment results in conjunction with fault trees of complex building systems to provide a probabilistic estimate about the percent of the inaccessible functional area within a building and to identify building components that impair its functionality. To facilitate functionality analysis, the research proposes a fault tree for a complex building system and introduces user-defined probabilistic limit state functions of individual building components that define the damage thresholds for partial (local) and full loss of the building functionality. A comprehensive, probabilistic repair time method is developed in collaboration with general contractors to realistically reflect current construction practices. The method utilizes the critical path method (CPM) to calculate the total duration of repair project, where repair and resources are scheduled based on the sporadic spatial distribution of damage accounting for surge in construction demand and labor congestion. It consists of two components: (1) the repair scheduling method; which can accommodate any repair sequencing and considers realistic labor allocations; and (2) the resource scheduling method; which provides an efficient way of reducing workers during labor congestions while minimizing its prolonging effect on the project duration. The mobilization time method proposes new algorithm for evaluation of mobilization time (time between the closure of a facility and the beginning of repairs) that is based on published research and data collected by interviewing general contractors, building inspectors, structural engineers, and facility managers. The unique feature of the method is its capability to derive different building limits states (i.e., the repairability limit state, detailed inspection limit state, and functionality limit state) and to use them to determine mobilization activities on a project and associated mobilization times. The distinguishing feature of the framework is its capability of generating the recovery curve and isolating the main contributors to the interrupted building operation and recovery process. This is demonstrated in the case study of an existing 13-story office building. Importantly, the outcomes of the study showcase how these unique recovery-based results can be effectively used as a guide for the development of earthquake mitigation strategies and design/retrofit solutions to improve seismic performance.