Roof Overhang Wind Pressure

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.

Roof overhang wind pressure.

Purlins c c roof pressure from 30 4 2b the effective wind pressures for zones 1 2 and 3 can be determined. 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. Wall 27 5 psf roof 6 5 psf end zone. In order for a structure to be sound and secure the foundation roof and walls must be strong and wind resistant.

Kz is velocity pressure exposure coefficient. Since trusses are spaced at 26ft hence this will be the length of purlins. 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. Effective wind area 225 33 sq ft.

Qz 0 613 kz kzt kd v2 n m 2. 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. The effective wind area should be the maximum of. 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.

Qz 0 00256 kz kzt kd v2 lb ft 2 or. Wind induces suction almost over the entire pyramidal roof of square plan building models for all roof slopes i e. For the leeward overhang the coefficient for the leeward wall c p 0 5. Acting on the bottom surface of the overhang in combination with pressures acting on the top surface.

Effective wind area 26ft 2ft or 26ft 26 3 ft 52 ft 2 or 225 33 sq ft. Overhangs on the leeward and side edges shall have the basic zone pressure applied. Mwfrs roof overhang pressures asce 7 only addresses the windward overhang specifying the use of a positive pressure coefficient of c p 0 8. This procedure addresses roof overhangs via footnote 8 on figure 28 6 1.

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.