Probabilistic Prediction of Post-disaster Functionality Loss of Community Building Portfolios Considering Utility Disruptions
I am proud to announce that the latest collaborative work from the CORE lab has been accepted for publication in the ASCE’s Journal of Structural Engineering. The new paper title is a mouthful, “Probabilistic Prediction of Post-disaster Functionality Loss of Community Building Portfolios Considering Utility Disruptions”, but the researchers (Weili Zhang, Peihui Lin, Naiyu Wang, Charles Nicholson, and Xianwu Xue) have been just calling the effort the “PPPD” project.
The study proposes a framework for the probabilistic prediction of building portfolio functionality loss in a community following an earthquake hazard. Building functionality is jointly affected by both the structural integrity of the building itself and the availability of critical utilities.
To this end, the framework incorporates three analyses for a given earthquake scenario:
- evaluation of the spatial distribution of physical damages to both buildings and utility infrastructure
- computation of utility disruptions deriving from the cascading failures occurring in the interdependent utility networks; the cascading failures are simulated by use of new mixed-integer, multicommodity network flow optimization model
- by integrating (1) and (2), a probabilistic prediction of the post-event functionality loss of building portfolios at the community scale.
The framework couples functionality analyses of physical systems of distinct topologies and hazard response characteristics in a consistent spatial scale, providing a rich array of information for community hazard mitigation and resilience planning.
An implementation of the framework is illustrated using the residential building portfolio in Shelby County, TN, subjected to an earthquake hazard. A single realization of an earthquake scenario in Shelby Country, TN is depicted below.
Since the building damage, the flow model, the data collection/aggregation can all be complted efficiently, it is easy to extend the single simulation realization to many realizations. This allows for a spatial probabilistic analysis of the vulnerabilities in the affected area. The figure below depicts the expected impact to the region based on 1,000 simulations of the scenario earthquake.
The intricacies that relate how the electric power network (EPN) support the potable water network (PWN), along with the particular individual component vulnerabilities of the EPN and PWN, produce probabilistic failure patterns in building functionality (see sub-figure d. above), that are not obvious!
RUO and RFL
Additionally, the framework allows us to compare a more traditional building portfolio analysis to with that of the practical implications of disruptive events. That is, even if your place of employment is not damaged, if the building does not have power or water, then it will be closed for business anyway!
The green line in the figure to the right denotes the probability of exceedance for the ratio of buildings which cannot be occupied (RUO) due to physical damage. The dotted line relates to the ratio of functional loss of buildings (RFL) which is due to any combination of direct damage and utility loss. Clearly, the RUO is a conservative estimate compared to RFL. For example, there is only a 40% chance that 40+% of the buildings will be directly damaged to the extent of restricted occupancy. However, that number jumps to 80% when the utilities are considered!
This work represents a wonderful collaborative effort within the CORE lab. Weili Zhang developed the interdependency model and worked closely with Peihui Lin, who provided the building analyses. And both worked closely with Xianwu Xue, the GIS expert. And of course, I am always pleased to work with my colleague Naiyu Wang in Civil Engineering. We have much, much collaborative work already in-progress and planned for the future!