The following word and term shall, for the purposes of this appendix, have the meaning shown herein.
SCREEN ENCLOSURE. A building or part thereof, in whole or in part self-supporting, and having walls of insect screening, and a roof of insect screening, plastic, aluminum or similar lightweight material.
DESIGN WIND PRESSURES FOR SCREEN ENCLOSURE FRAMINGa, b, e, f, g, h
|LOAD CASE||WALL||ULTIMATE DESIGN WIND SPEED,Vult (mph)|
|Exposure Category B Design Pressure (psf)|
|Ac||Windward and leeward walls (flow thru) and windward wall (nonflow thru) L/W = 0-1||6||7||8||9||11||13||14||16||18||21|
|Ac||Windward and leeward walls (flow thru) and windward wall (nonflow thru) L/W = 2||7||8||9||11||12||14||16||19||21||24|
|Bd||Windward: Nongable roof||9||10||11||13||15||18||21||23||26||30|
|Bd||Windward: Gable roof||11||13||14||16||19||22||26||29||33||37|
For SI: 1 mile per hour = 0.44 m/s, 1 pound per square foot = 0.0479 kPa, 1 foot = 304.8 mm.
- Design pressure shall be not less than 10 psf in accordance with Section AH106.4.1.
- Loads are applicable to screen enclosures with a mean roof height of 30 feet or less in Exposure B. For screen enclosures of different heights or exposure, the pressures given shall be adjusted by multiplying the table pressure by the adjustment factor given in Table AH106.4(2).
- For Load Case A flow thru condition, the pressure given shall be applied simultaneously to both the upwind and downwind screen walls acting in the same direction as the wind. The structure shall also be analyzed for wind coming from the opposite direction. For the nonflow thru condition, the screen enclosure wall shall be analyzed for the load applied acting toward the interior of the enclosure.
- For Load Case B, the table pressure multiplied by the projected frontal area of the screen enclosure is the total drag force, including drag on screen surfaces parallel to the wind, that must be transmitted to the ground. Use Load Case A for members directly supporting the screen surface perpendicular to the wind. Load Case B loads shall be applied only to structural members that carry wind loads from more than one surface.
- The roof structure shall be analyzed for the pressure given occurring both upward and downward.
- Table pressures are MWFRS loads. The design of solid roof panels and their attachments shall be based on component and cladding loads for enclosed or partially enclosed structures as appropriate.
- Table pressures apply to 20-inch by 20-inch by 0.013-inch mesh screen. For 18-inch by 14-inch by 0.013-inch mesh screen, pressures on screen surfaces shall be permitted to be multiplied by 0.88. For screen densities greater than 20 inches by 20 inches by 0.013 inch, pressures for enclosed buildings shall be used.
- Linear interpolation shall be permitted.
Structural members supporting screen enclosures shall be designed to support the minimum wind loads given in Tables AH106.4(1) and AH106.4(2) for the ultimate design wind speed, Vult, determined from Figure AH106.4.1. Where any value is less than 10 pounds per square foot (psf) (0.479 kN/m2) use 10 pounds per square foot (0.479 kN/m2).