Study of Wind Loads on Porous Hyperbolic Paraboloid Free Roofs
1Study of Wind Loads on Porous Hyperbolic Paraboloid Free Roofs
The objective of the present 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 based on a wind tunnel experiment, in which solid and porous models are used. The thickness of the models is only 1 mm. The porous model has a number of small circular holes. The porosity is changed from 0 (solid) to 0.4. The geometric parameters under consideration are the rise-to-span (or sag-to-span) ratio and the slope. A six-component force balance in a turbulent boundary layer is used to determine the overall aerodynamic forces and moments operating on a model. Based on a combination of the lift and aerodynamic moment coefficients, the design wind force coefficients, CNW* and CNL*, for the windward and leeward halves of the roof are proposed for diagonal wind directions. Focus is on the axial forces induced in the columns as the load effect for discussing the design wind loads, assuming that the roof is rigid and simply supported by four corner columns. It is found that the porosity reduces the wind loads on the roof significantly. The design wind force coefficients for a porous roof can be obtained by those for a solid roof with the same configuration multiplied by a reduction factor. The proposed wind force coefficients are validated by comparing the load effect predicted by the proposed wind force coefficients with the maximum load effect obtained from a dynamic analysis using the time history of lift and aerodynamic moment coefficients obtained from the wind tunnel experiment.
#hyperbolic #paraboloid #free #roof #porosity #wind #tunnel #experiment #main #force #resisting #system #coefficient