Tornadoes occur at a high frequency in the United States compared with other natural hazards but have a substantially small footprint. A single high-intensity tornado can result in high casualty rates and catastrophic economic and social consequences, particularly for small- to medium-size communities. Comprehensive community resilience assessment and improvement requires the analyst to develop a model of interacting physical, social, and economic systems and to measure outcomes that result from specific decisions made. These outcomes often are in the form of metrics such as the number of people injured or the number of households and/or businesses without water, but it has been recognized that most community resilience metrics have socioeconomic characteristics. In this study, for the first time, a fully quantitative interacting model is used to examine the effect of a tornado damaging physical infrastructure (buildings and electrical power network) and the effects on the population and the local economy for a real community. Then, three residential building retrofit strategies are considered as alternatives to improve community resilience, and the metrics for the physical, economic, and social sectors are computed. An illustrative example is presented for the 2011 Joplin tornado in a new open-source Interdependent Networked Community Resilience Modeling Environment (IN-CORE), with a computable general equilibrium (CGE) economics model that computes household income, employment, and domestic supply before and after the tornado. Detailed demographic data was allocated to each structure to enable the calculation of resilience metrics related to population dislocation impacts from the tornado. The results of these analyses stemming from building damage estimation have a logical trend, but the substantial contribution of this work is that, for the first time, the effect of retrofit strategies for tornado loading can be quantified in terms of their effects on socioeconomic metrics.

The retrofit of wood-frame residential buildings is a relatively effective strategy to mitigate damage caused by windstorms. However, little is known about the effect of modifying building performance for intense events such as a tornado and the subsequent social and economic impacts that result at the community level following an event. This paper presents a method that enables a community to select residential building performance levels representative of either retrofitting or adopting a new design code that computes target community metrics for the effects on the economy and population. Although not a full risk analysis, a series of generic tornado scenarios for different Enhanced Fujita (EF) ratings are simulated, and five resilience metrics are assigned to represent community goals based on economic and population stability. To accomplish this, the functionality of the buildings following the simulated tornado is used as input to a computable general equilibrium (CGE) economics model that predicts household income, employment, and domestic supply at the community level. Population dislocation as a function of building damage and detailed sociodemographic US census-based data is also predicted and serves as a core community resilience metric. Finally, this proposed methodology demonstrates how the metrics can help meet community-level resilience objectives for decision support based on a level of design code improvement or retrofit level. The method is demonstrated for Joplin, Missouri. All analyses and data have been developed and made available on the open-source IN-CORE modeling environment. The proposed multidisciplinary methodology requires continued research to characterize the uncertainty in the decision support results.

From December 10 to December 11, 2021, a deadly tornado outbreak struck across several states in the US, including Arkansas, Illinois, Kentucky, and Tennessee. This tornado outbreak resulte...

This paper presents a failure analysis of pot-type bearings on the West 8th Avenue viaduct in Denver, Colorado, and aims at determining the causes of guide bar fracture, polytetrafluoroethylene (PTFE) peeling, and steel–steel grind. All the failure modes of the pot-type bearings resulted from the thermal response of this structure. Two finite-element models were applied in this study. One model was developed using SAP 2000 to examine the thermal effect, including transverse and longitudinal movement and vertical pressure. The other model was developed using ANSYS software and emphasized contact analysis based on stress and displacement contour plots. The purpose was to demonstrate how the components of the bearing structure interact when subjected to the movement and stress transferred from the superstructure. The results indicated that when the upper steel plate of the bearing was subjected to transverse and longitudinal movement, the excessive movement caused the guide bar to hit the steel pot. The lateral slippage of the two components occurred simultaneously, leading to the generation of steel–steel grind of the two components. Extremely large-edge contact stresses arose from the eccentrical loading on the PTFE, resulting in PTFE wear and peeling in the long term. Because the steel pot resisted the intermediate section of the guide bar, the guide bar was laterally bent. Initial cracking was induced, and low cycle fatigue loading accelerated the crack expansion in a radial plane until the guide bar fractured.