Roof Overhang Wind Pressure

Kz is velocity pressure exposure coefficient.

Roof overhang wind pressure.

For the leeward overhang the coefficient for the leeward wall c p 0 5. Where zone e or g falls on a roof overhang on the windward side of the building use eoh and goh f or the pressure on the horizontal projection of the overhang. When building a structure it is important to calculate wind load to ensure that the structure can withstand high winds especially if the building is located in an area known for inclement weather. Since trusses are spaced at 26ft hence this will be the length of purlins.

The effective wind area should be the maximum of. Effective wind area 26ft 2ft or 26ft 26 3 ft 52 ft 2 or 225 33 sq ft. Mwfrs roof overhang pressures asce 7 only addresses the windward overhang specifying the use of a positive pressure coefficient of c p 0 8. 0 10 20 and 30 and the highest negative area weighted pressure coefficient was found to be 0 540 for 10 roof slope with 0 wind incidence angle on face a.

Canopies with less than 50 obstructions below the roof surface would be considered clear. Wall 41 2 psf roof 11 7 psf. In order for a structure to be sound and secure the foundation roof and walls must be strong and wind resistant. Qz 0 613 kz kzt kd v2 n m 2.

Wall 27 5 psf roof 6 5 psf end zone. Overhangs on the leeward and side edges shall have the basic zone pressure applied. Overhangs roof truss tails zone 2 p 20 1 2 2 44 2 psf use trib area of tail zone 3 p 20 1 2 5 50 3 psf roof deck at overhangs zone 2 p 20 1 2 2 44 2 psf zone 3 p 20 1 3 7 74 4 psf. Wind induces suction almost over the entire pyramidal roof of square plan building models for all roof slopes i e.

Qz 0 00256 kz kzt kd v2 lb ft 2 or. Acting on the bottom surface of the overhang in combination with pressures acting on the top surface. Windward parapet 0 0 psf gcpn 1 5 windward roof leeward parapet 0 0 psf gcpn 1 0 overhangs 20 6 psf upward add to windward roof pressure horizontal mwfrs simple diaphragm pressures psf transverse direction normal to l interior zone. Effective wind area 225 33 sq ft.

Obstructed wind flow is considered when 50 or more of the area below the surface of the roof is composed of objects inhibiting wind flow such as a canopy atop a concrete basin at a wastewater treatment plant.