Sections 29.5 and 29.5.1 of ASCE 7 shall be modified as follows:
29.5 Design wind loads: Other structures. 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:
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).
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 A r 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 ft2 (m2).