Roof Overhang Wind Pressure

Wind induces suction almost over the entire pyramidal roof of square plan building models for all roof slopes i e.

Roof overhang wind pressure.

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. Mwfrs roof overhang pressures asce 7 only addresses the windward overhang specifying the use of a positive pressure coefficient of c p 0 8. Qz 0 00256 kz kzt kd v2 lb ft 2 or. Overhangs on the leeward and side edges shall have the basic zone pressure applied.

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. This procedure addresses roof overhangs via footnote 8 on figure 28 6 1. The effective wind area should be the maximum of. For the leeward overhang the coefficient for the leeward wall c p 0 5.

Kz is velocity pressure exposure coefficient. Wall 41 2 psf roof 11 7 psf. Effective wind area 26ft 2ft or 26ft 26 3 ft 52 ft 2 or 225 33 sq ft. 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.

Acting on the bottom surface of the overhang in combination with pressures acting on the top surface. Canopies with less than 50 obstructions below the roof surface would be considered clear. Effective wind area 225 33 sq ft. In order for a structure to be sound and secure the foundation roof and walls must be strong and wind resistant.

Purlins c c roof pressure from 30 4 2b the effective wind pressures for zones 1 2 and 3 can be determined. Wall 27 5 psf roof 6 5 psf end zone. Qz 0 613 kz kzt kd v2 n m 2. The velocity pressure is depending on wind speed and topographic location of a structure as per the code standard velocity pressure q z equivalent at height z shall be calculated as.

Since trusses are spaced at 26ft hence this will be the length of purlins.