Abstract
: Numerous post-windstorm investigations have reported that windborne debris can cause costly damage to the envelope of buildings in urban areas under strong winds (e.g., during hurricanes or tornados). Thus, understanding the physics of debris flight is of critical importance. Previously developed numerical models describing debris flight physics have not been validated for the complex urban flow environment; such a validation requires experimentally measuring the debris flight trajectory in wind tunnel tests. In this context, this paper proposes a debris measurement algorithm using stereophotogrammetry. This algorithm aims to determine the six-degree-of-freedom (6-DOF) trajectory and velocity of flying debris, addressing the research gap, i.e., the lack of an algorithm/software for measuring three-rotational-DOF using stereophotogrammetry. This is a civil engineering problem, but computer graphics is the foundation to solve it. This paper focuses on the theoretical development of the algorithm. The developed algorithm can be readily implemented in modern wind tunnel experiments.
Highlights
Windborne debris damage to the cladding and façades of buildings has been identified as a major contributor to damage in urban areas after windstorms in numerous studies [1,2,3,4,5,6,7,8,9,10,11]
Such a validation first requires the measurement of the debris flight trajectory in a 3D field in wind tunnel tests
For simplicity in the notation for time history of the plate trajectory determined from vertices reconstructed using stereopairs, the 3D plate is represented as a frame F(t) at time t that contains both the position and the orientation for the plate
Summary
Windborne debris damage to the cladding and façades of buildings has been identified as a major contributor to damage in urban areas after windstorms (e.g., hurricanes, tornados, thunderstorms) in numerous studies [1,2,3,4,5,6,7,8,9,10,11]. Experimental validation of the numerical debris flight model for an urban built environment is critical for understanding complex debris flight behavior and predicting the debris impact location, energy/momentum, and the damage state of the building envelope components Such a validation first requires the measurement of the debris flight trajectory in a 3D field in wind tunnel tests. DTinhgenpitxheel tlwocoatcioanmsefroarstwaroe huisgehd-stpoemedecaasmureeratsh;eit2cDancoboerrdeimnaotveesdoofntcheetphreocjealcitbiroantioonf flisying decbormispolentetdh.eTghreindtwheatlwl boycalimghertasseamreanuasetidntgofmroemasuthreetchaem2Deracoloorcdaitnioatness.oUf tshine gprtohjeecstitoenreoofpfalyirinogf 2D codoerdbrinisatoens (tih.ee.,Fd)1o, fh1t,hde2,dhe2brmise, agsiuverendthbeyrtehleattiwveolcoacmatieornass)ooffththeetwdeobcraism, wereastrtyo ttohedegtreidrmwinalel b(io.et.h, the podsitainodn (lth).ree-translational-DOF, x, y, z) and orientation (three-rotational-DOF) of the debris, given the relative locations of the two cameras to the grid wall (i.e., d and l) This problem will be solved in two steps: First, for a single compact piece of debris, considered as a point object (only three-translation-DOF is considered), for rigid body thin plate debris. We need to determine the 3D position of the debris, i.e., x, y, and z, in terms of these parameters
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