12906 19TH AVE SE FRED MEYER FUELING STATION 2018-01-02 MF Import

ASCE M Ce = 1.2 Exposure Factor as determined from Table 7-2 Ct = 1.2 Thermal factor as determined from Table 7-3 D = Snow Density in pcf as determined from Eq. 7-4 hb = Height cf balanced snow load determined by dividing Pf by D, in feet. hd = Height of snow drift, in feet he = Clear height from top of balanced snow to top of parapet, ft hr = 3.08 = Fascia height, ft I = 1.0 = Importance factor (see Table 7-4). Pf = Snow load on flat roofs, psf. Pg = 25 =ground snow, psf. Pd = Maximum intensity of drift surcharge load, psf. lu = 24 = Length of roof upwind of the drift, feet w = Width of snow drift, in feet Section 7.3--Flat-Roof Snow Loads, Pf The snow load, Pf, on a roof with a slope equal to or less than 5' shall be calculated in psf using equation 7-1, but not less than the following mimimum values fcr low slope roofs: where Pg is 20 psf or less Pf = I(Pg), where Pg exceeds 20 psf, Pf = 20 (1). Section 7.7 & Section 7.8 The geometrey of the surcharge load due to snow: drifting shall be approximated by a triangle as shown in figure 7-8. Drift loads shall be superimposed on the balanced snow load. If he/hb is less than 0.2, drift loads are not required to be applied. The height of such drifts shall be taken as 0.75 x hd as determined from Fig 7-9, with lu equal to the length of the roof upwind of the projection or parapet wall. If the side of a roof projection is less than 15 it long, a drift load is not required to be applied to that side. If the height, hd, is equal to or less than hc, the drift width shall equal 4hd and the ddl height shall equal hd. If this height exceeds hc, the drift width, w, shall equal 4 hdz/hc and the drift height shall equal hc. However, the drift width w shall not exceed 8hc. The maximum intensity of the drift surcharge load, pd, equals hd x D where the snow density, D, is defined by Eq 74. Section 7.10--Rain-On-Snow Surcharge Load For locations where Pg is 20 psf or less but not zero, all roofs with a slope less than 1 /2 hill, shall have a 5 psf rain -on -snow surcharge load appled to establish the design snow loads. Where the minumum flat roof design snow loadfrc,n Section 7.3.4 exceeds Pf as determined by eq. 7-1, the rain -on -snow surcharge load shall be reduced by the difference between these two valuos with a maximum reduction of 5 psf. Pf= 0.7 x Ce x Ct x I x Pg Eq 7-1 Pf = 25.0 psf hd = 0.75 x (0.43(lu)A1/3 x (Pg+10)A1/4-1.5) Ref. Fig. 7-9 hd = 1.14 ft D= 0.13Pg + 14 < 30 psf Eq 7-4 w D = 17.25 psf w hb = 1.45 ft he =hr-hb = 1.63 ft -ter he/hb = 1.13 Consider Drift hd" LPf _/ r7RIFTSURCHARGE w = 4.55 ft hn FIGURE 7-8 Pd = D x hd<D x he Configuration of Snow Drifts on Lower Roofs Pd = 19.62 psf hC I 1 hr 09/10/2008 39089.123 Page 2 of 20