ISRM 2023 - PUBLICATIONS

Keynote lectureNiketa UKAJ, Christian HELLMICH, Stefan SCHREINERInstitute for Mechanics of Materials and Structures, TU Wien, Vienna, AustriaThe Mechanics of Pandemics: Empowering Boltzmann creep for the prediction of COVID-19 fatality trendsEver since Boltzmann’s landmark paper from 1874, integro-differential equations for viscoelasticity have been a cornerstone for reliable quantification of the time-dependent response of solid mechanical systems: their creep strains depend on the accumulated effect of all load events having taken place before. This naturally includes rock mechanics, both as regards its narrower meaning of rock creep testing, and its broader sense of creeping tunnel support systems such as shotcrete shells in the context of the New Austrian Tunneling Method. When the COVID-19 pandemic evidenced often sobering performance of traditional epidemiological models [where the system response only depends on the current state of the system, and not on the entire history], the question arose whether the Boltzmann integro-differential equations may be as efficient for “virus loads”, as they have proved to be for classical mechanical loads. Evaluating infection and fatality data from more than 100 countries, this question was affirmatively answered. Here we go one step further, and discuss recently obtained results for “aging pandemics” in analogy to aging creep experienced in shotcrete systems where the material maturation due to the hydration reaction evolves at a similar pace as the creep strains do. We observe exponentially decaying fatality rates throughout the first thousand days of the COVID-19 pandemic, with a characteristic time of around 180 days in the case of Austria. | SARS-CoV-2, COVID-19, concrete creep, viscoelasticity, integro-differential equations, optimization