| Summary |
Design wind force coefficients for H.P.-shaped porous canopy roofs have been investigated based on a series of wind tunnel experiments. The roof models were made of 1mm thick perforated plastic plates, the porosity of which was changed from 0 (solid) to 0.4. Overall aerodynamic force and moment coefficients were measured in a turbulent boundary layer with a six-component force balance for various wind directions. The flow around the solid roof model was visualized by using an oil-film method. When the wind direction is parallel to a diagonal connecting the low points of the roof, the wind flows along the upper surface of the roof without separation. On the other hand, when the wind direction is parallel to a diagonal connecting the high points, a pair of conical vortices is generated along the windward edges of the roof. For these wind directions, the peak values of lift and aerodynamic moment coefficients become larger. These peak values are mainly caused by the wind speed fluctuations of approach flow. The wind loads on canopy roofs generally decrease with an increase in porosity, or a decrease in pressure loss coefficient of the roof. Based on these results, the design wind force coefficients are proposed as a function of sag-to-span ratio and the porosity for the two wind directions parallel to the diagonals of the roof. |