Sections 29.5 and 29.5.1 of ASCE 7 shall be modified as follows:
The design wind force for other structures (chimneys, tanks, similar structures, open signs, lattice frameworks and trussed towers) whether ground or roof mounted, shall be determined by the following equation:(29.4-1)
qz = velocity pressure evaluated at height z as defined in Section 29.3, of the centroid of area Af;
G = gust-effect factor from Section 26.9;
Cf = force coefficients from Figures 29.5-1 through 29.5-3; and
Af = projected area normal to the wind except where Cf is specified for the actual surface area, in square feet (m2).
29.5.1 Rooftop structures and equipment for buildings.
The lateral force, Fh for rooftop structures and equipment shall be determined as specified below.
GCr = 1.9 for rooftop structures and equipment with Af less than (0.1Bh). (GCr) shall be permitted to be reduced linearly from 1.9 to 1.0 as the value of Af is increased from (0.1Bh) to (Bh);
qh = velocity pressure evaluated at mean roof height of the building; and
Af = vertical projected area of the rooftop structure or equipment on a plane normal to the direction of wind, in square feet (m2).
The vertical uplift force, Fv, on rooftop structures and equipment shall be determined from Equation (29.5-3).
GCr = 1.5 for rooftop structures and equipment with Ar less than (0.1BL). (GCr) shall be permitted to be reduced linearly from 1.5 to 1.0 as the value of Ar is increased from (0.1BL) to (BL);
qh = velocity pressure evaluated at the mean roof height of the building; and
Ar = horizontal projected area of rooftop structure or equipment, in square feet (m2).
Exception: Exposed mechanical equipment or appliances fastened to a roof or installed on the ground in compliance with the code using rated stands, platforms, curbs, slabs, walls, or other means are deemed to comply with the wind-resistance requirements of the 2007 Florida Building Code, as amended. Further support or enclosure of such mechanical equipment or appliances is not required by a state or local official having authority to enforce the Florida Building Code.