Stress-strain capacity analysis for the impact of natural disasters on coupled infrastructure facilities
Infrastructure facilities serve as the backbone of the communities and industries by sustaining social and economic activities through their services. However, the physical impact of a disaster can have an adverse effect on the functioning of the infrastructure. In addition, the affected infrastructure facilities are unable to adequately meet the needs of the community immediately after the disaster. Thus, to compensate for gaps in services, infrastructure facilities are likely to run their systems, such that it puts additional stress on their resources that exceeds their designed capacities at the expense of level of service. For example, after the devastating earthquake in Haiti in 2010, disrupted utility services, limited available road networks, and the lack of civic governance influenced the capacity of all essential service providers such as hospitals. Furthermore, the hospitals that were impacted by the earthquake had limited resources, such as water and power utility for operating the hospitals, beds for patients, medical staff, and medical supplies, to meet the increased health needs of the community. As a result, the hospitals in Haiti had to put excessive stress on their available resources, as their remaining capacities were not enough to accommodate the increased number of patients without assistance from NGOs or other external entities. If the emergency managers of the hospitals were able to evaluate their remaining capacities based on the excessive stress so that they could make appropriate strategies for mitigating the excessive stress ahead of time, the infrastructure facility would have serviced the affected communities more efficiently. This research proposes a framework that can be used to understand and evaluate the strain capacities based on the stress imposed on an infrastructure facility under varying post-disaster conditions. A new principle to assess the stress level in a post-disaster infrastructure facility was developed using the analogy of the stress-strain concept in the mechanics of materials. In this research, the definitions of the stress and strain in an infrastructure facility are adapted in order to reflect the ability of a post-disaster infrastructure to provide essential service. Since an infrastructure facility is composed of various infrastructure units that are either tightly or loosely coupled through their exchange of services for the facility, the analysis of stress and strain of an infrastructure facility requires understanding of complex interdependent systems. As such, using the system-of-systems approach, a stress and strain assessment tool (SSAT) for a post-disaster infrastructure was developed based on the proposed stress-strain principle. Using the discrete event simulation method, the developed SSAT was applied to a case of healthcare facility under an earthquake scenario to demonstrate its implementation to post-disaster infrastructure systems. As a coupled system, water and electricity resources of the healthcare facility were considered besides its medical resources. While running the simulation, the dynamic strain capacities of the hospital, caused by the disruption of the linked external infrastructure, i.e., water and power units, are measured with respect to the applied stress. This enables emergency managers to evaluate the available strain capacities of the infrastructure units based on the imposed stress. Eventually, the SSAT would assist in developing appropriate strategies for mitigating excessive stress on infrastructure units in natural disaster situations.
Hastak, Purdue University.
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