Based on a wind tunnel experiment using solid and porous models, the goal of this study is to propose wind force coefficients for designing the main wind force resisting systems of porous hyperbolic paraboloid (HP) free roofs with square plan. The models have a thickness of only 1 mm. A number of small circular holes can be found in the porous model. The porosity has been increased from 0 (solid) to 0.4. The rise-to-span (or sag-to-span) ratio and slope are the geometric parameters under consideration. To determine the overall aerodynamic forces and moments operating on a model, a six-component force balance in a turbulent boundary layer is used. For diagonal wind directions, the design wind force coefficients, CNW* and CNL*, for the windward and leeward halves of the roof are proposed based on a combination of the lift and aerodynamic moment coefficients. For discussing the design wind loads, the focus is on the axial forces induced in the columns as the load effect, assuming that the roof is rigid and simply supported by four corner columns. It has been discovered that porosity significantly reduces wind loads on the roof. The design wind force coefficients for a porous roof can be calculated by multiplying the coefficients for a solid roof with the same configuration by a reduction factor.
Author (s) Details
Yasushi Uematsu
National Institute of Technology (KOSEN), Akita College, Akita 011-8511, Japan.
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