Experimentally estimating wind load coefficients for tornadoes – An alternative perspective

Abstract

Given the increased interest in tornado-induced wind loading (in part exhibited by inclusion of such loading in wind standards around the world) it is vital to understand the various characteristics of such loading and their relative overall importance. As such, employing a range of types of simulations and simulators would be helpful for understanding and estimating tornado-induced wind load coefficients. This paper advocates a quasi-steady framework to estimate tornado-induced wind loads and identifies the tornado flow characteristics most likely to influence these loads. The flow characteristics discussed include the flow field itself, the static pressure field, vortex translation, flow turbulence, streamline curvature, and flow acceleration. A fundamental conclusion of this paper is that pressure coefficients for tornado-induced wind loading should always be measured and reported as functions of these characteristics. The paper discusses various alternatives for simulating these characteristics and highlights which types of facilities would be effective for studying each one. Such approaches will also require deliberately measuring velocity and static pressure simultaneously with any load measurements made on a building model. This will then help clarify the dependencies of pressure and load coefficients to the various parameters, will limit the parameter space that must be explored to understand extreme loading, and will facilitate easier comparison among different laboratory results, all of which will ultimately lead to improved design standards.