Date of Graduation

5-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Civil Engineering

Advisor

R. Panneer Selvam

Committee Member

Micah Hale

Second Committee Member

Rick J. Couvillion

Third Committee Member

Ernie Heymsfield

Abstract

Tornadoes induce very different wind forces than a straight-line (SL) wind. A suitably designed building for a SL wind may fail when exposed to a tornado-wind of the same wind speed. It is necessary to design buildings that are more resistant to tornadoes. Most studies have been conducted to investigate tornado forces on cubic, gable-roof and cylinder buildings. However, little attention has been paid to investigate tornado force on dome buildings; hence, further research is conducted in this study. The forces on a dome, cube and prisms were analyzed and compared using Computational Fluid Dynamics (CFD) for tornadic and SL winds. One typical tornado parameter was considered for comparison. The conclusions drawn from this study were illustrated in visualizations. The tornado force coefficients on the cube and prisms were larger than those on the dome by at least 90% in the x-y directions, and 140% in the z direction. The tornado pressure coefficients on cube and prisms were greater at least 200%. The force coefficients on cube and prisms due to SL wind were higher than those on the dome due to tornado wind by about 100% in the z-direction.

The ratio of tangential (Vθ) to translational (Vt) velocity reported in recent studies is 10 or greater, which is larger than the field observation ratios. The influence of Vθ/Vt ratios on the tornado force coefficient for a cubic, prism and dome buildings were compared using a systematic study. The Vθ/Vt ratios were considered to be 1, 3, 6, and 8 for comparison. These ratios were very much in agreement with field observation ratios. The magnitudes of the forces were found to be larger for slower translation speed or higher Vθ/Vt ratios. For faster translation speeds or, lower Vθ/Vt ratio, the maximum force coefficients shifted to the left of the time history.

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