A typical house is therefore designed to withstand just 62% of the forces a strong EF-2 tornado will produce. The vast majority of those buildings are light-framed wood structural systems ( van de Lindt John and Dao Thang, 2009), that are prescriptively designed for 115 mph 3 s gust basic wind speeds in most tornado-prone regions of the United States. Thus, single-family residential buildings remain highly exposed and at risk of catastrophic damage from tornadoes. Only recently has there been any effort to apply engineering knowhow to improve the tornado-resilience of buildings. The life-saving activities of the Federal Emergency Management Agency and some states provided grants to construct in-home and in-school tornado shelters that protect many against loss of life and injuries in tornadoes ( Herseth et al., 2017). The research to improve forecasting of major tornado activity of the National Weather Service has, since 1950, improved tornado warning lead times, reducing the numbers of tornado-related fatalities and injuries ( NSSL, 2013). These most costly tornado and hurricane events caused just 1,270 and 6,507 fatalities, respectively ( NOAA National Centers for Environmental Information (NCEI), 2020). This figure is lower but of a comparable order of magnitude to hurricane-related losses of nearly $1 Trillion dollars ($954 Billion) over the period 1980–2019 from 45 hurricanes. billion-dollar disaster” events (plus many thousands of less-costly events) involving tornadoes spawned by severe storm in the United States over the past 40 years (since 1981). There has been $130 Billion (CPI-adjusted estimate) losses due to 54 “U.S. Economic losses from tornadoes are still high. These remarkably low fatality numbers are partly due to good outcomes of meteorological and engineering research, and partly to good fortune that more tornadoes had not directly affected our largest cities and residential communities. tornado-related fatalities are <100 per year ( NWS, 2020) and the average tornado-caused annual economic losses are between $4.7B and $7.2B ( Simmons et al., 2013) no more than 1–3% of the annual Gross Domestic Products of the most-affected states. This was by far the highest death toll from tornadoes since the 1950s. In the United States, 2011 was an outlier tornado year in which 1,700 tornadoes occurred with 560 tornado-related deaths. More research to further our understanding of tornado-induced wind loads and wind-borne debris effects is needed to increase confidence in its application to any tornado and any city. The Tool could be used by a community to model any tornado path and/or size and estimate future damage. It was found the ETDA Tool provides reasonable agreement with the field damage observations to houses. The paper explains the methodology of the approach and presents results comparing hindcast damage ratios against observed values of field-observations collected after a tornado strike on residential communities in Garland/Rowlett, TX. The output of the EDTA Tool is presented as series of mean damage ratios, and other statistics quantifying tornado-damage caused, plotted against distance away from the tornado vortex centerline. The ETDA Tool was developed around a Monte Carlo simulation engine, using theoretical models for tornado wind velocity and pressure drop in the tornado vortex, as well as experimentally-determined probability distribution functions for the structural resistances of eight building component systems selected to describe the structure. The research developed a numerical estimation model to aggregate damage that a specified tornado would cause to the residential wood-framed structures in a community. The research is motivated by the need for the public to visualize the extent of tornado vulnerabilities of residential buildings in our communities. The objective is to determine the predictive capability of an engineering-based tornado damage-assessment (ETDA) Tool using published building damage observations captured by the authors in a recent tornado.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |