Date of Award
Master of Science
Partha P. Sarkar
Nearly 1000 tornados are reported annually in the US. The annual damage caused by tornados can exceed one billion dollars. Of the damage caused, the most common and severely damaged structures are the conventional low-rise timber buildings which account for most of the residential buildings in the `tornado alley'; the central region of the country, where most tornados occur. Little research has been done to study the effects of tornados on low-rise buildings. To predict the behavior of a conventional low-rise timber building under a translating tornado, it is necessary to capture its interaction with the tornado. This work focuses on studying the interaction of a tornado with a low-rise building.
In the first part of the work, a methodology was developed to predict the load time histories experienced by a low-rise building under a translating tornado using the existing load coefficients of the building in straight line winds. The effects of tornado-building interaction and sudden pressure drop or suction acting on the outer surfaces of the building, due to the tornado vortex, were preserved in the methodology. For design and analysis of buildings it is very often necessary to obtain the load time histories in a tornado. The relative positions of the building and tornado in general are arbitrary. It would be impossible to experimentally determine the loads on the building for all eventualities. It would also be very expensive to even try to undertake such a study. The methodology shows that it is sufficient to predict the load time histories of a building with respect to any arbitrarily located tornado. The knowledge of tornado induced load time histories for a few building-tornado combinations is all that is needed. A gable-roofed building model with a square plan, geometrically scaled to 1:100, and a tornado of swirl ratio 1.14 were used for this study.
In the second part of this work, the interaction of a tornado with a one-story gable-roofed timber building (with a rectangular plan) was studied. The methodology presented here predicted the successive stages of structural damage caused to the building by a translating tornado as a result of its interaction with the building components. The dynamic effects of changing internal and external pressures on the building were taken into account, as the tornado translated past the building and inflicted damage. A partially damaged one-story building, located within the damage path of the Parkersburg tornado (May 25, 2008), was chosen for analysis using Finite Elements (FE). This tornado was rated EF5 by the National Weather Service. The observed damage was compared to that predicted in this study. The methodology described here enables accurate damage prediction and failure of a low-rise building from a tornado that will improve its component design and construction. Conversely, it also helps in assessing the intensity of a tornado from the observed damage state of the building.
Thampi, Hephzibah, "Interaction of a translating tornado with a low-rise builsing" (2010). Graduate Theses and Dissertations. 11765.