Tornado-Induced and Straight-Line Wind Loads on a Low-Rise Building With Consideration of Internal Pressure

Abstract

Tornado and straight-line wind events are often discussed and compared in terms of their intensity, e.g., maximum wind speed, however, it is unclear to what extent tornadoinduced and straight-line wind-induced wind loads are equivalent even for the same nominal intensity. This lack of understanding inhibits both tornado design philosophies and policies, and communication of tornado risk to the public. This study directly compares existing wind tunnel databases of tornado-induced and straight-line windinduced pressures, for a similar building model, to evaluate to what extent the induced surface pressures on a typical building differ. The existing datasets used in the study are enhanced with a numerical internal pressure model to facilitate the comparison across a range of opening configurations that would be common in typical buildings. The analysis finds that differences are most pronounced in the overall distribution of pressures across the building surface, and in the magnitudes of pressures in regions of strong flow separation. However, overall the magnitudes of the peak tornado-induced pressures are reasonably similar to straight-line wind-induced pressures, with tornadoinduced pressures on average 13% higher than equivalent straight-line wind-induced pressures. Ultimately, this study demonstrates a framework for such comparisons, while recognizing key sources of uncertainty and further research needs.

Engineering-Based Tornado Damage Assessment: Numerical Tool for Assessing Tornado Vulnerability of Residential Structures

“…The approach outlined above does not directly model the inertial effects of the internal pressure changes as discussed in Baker and Sterling (2018), and thus is likely to underestimate net tornadoinduced wind loads in buildings with minimal leakage through the building envelope. Previous research has shown however that most residential buildings either have sufficient background leakage, or incur damage to dominant openings, to enable rapid response of the internal pressure to external pressure changes (Roueche and Prevatt, 2013;Roueche et al, 2020). The ETDA Tool's Wind Field Module determines the magnitude and direction of wind speed at the house based on the distance from the tornado centerline.…”

Evaluation of tornado loads on double-sloped roofs at various ground roughness and positions by numerical Ward-type tornado simulation

“…The pressure magnitude in the area of strong flow separation and the overall pressure distribution on the building surface were both impacted by the vortex translation velocity. The pressure caused by a tornado was typically 13% higher than the pressure caused by a straight line of wind [1][2][3]. Volume-averaged velocity was proposed by [4], who discovered that it was the connection between tornadoes and linear wind-induced mean force.…”