SPECIFICATION FOR THE DESIGN OF - Transcon Steel

Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004 91
F8 Ridge Tension Strap Connection Requirement
Calculate the number of screws required for the ridge tension strap for a 24-foot span, 6:12
pitched roof subjected to 120 mph wind speed, Exposure Category C.
Calculate Wind Load
Per ASCE 7-1998 (ASCE, 1998):
Directionality Factor (K d )= 0.85 (Table 6-6)
Importance Factor = 1.0 (Section 6.5.5)
Topographic Factor (K zt )= 1.0 (Figure 6-2)
Velocity Exposure (K z ) = 0.98 (Table 6-5)
Velocity Pressure = q z = 0.00256 x K z x K zt x K d (V 2 x I) = 30.7077 (Eq. 6.5.10)
Pressure = p = q z [(GC pf ) – (GC pi )] (Eq. 6.5.12.2.1)
GC pf (Figure 6-4) CASE A
Roof Slope = 26.56 degrees
Area 1 Area 2 Area 3 Area 4 Area 1E Area 2E Area 3E Area 4E
0.550 -0.103 -0.447 -0.391 0.727 -0.196 -0.586 -0.536
GCpi (Figure 6-4) CASE A
Enclosed Buildings
+0.18 -0.18
GCpf (Figure 6-4) CASE B
Roof Slope = 26.56 degrees
Are
a 1
Area
2
Area
3
Area
4
Area
5
Area
6
Area
1E
Area
2E
Area
3E
Area
4E
Area
5E
Area
6E
-0.45 -0.69 -0.37 -0.45 0.4 -0.29 -0.48 -1.07 -0.53 -0.48 0.61 -0.43
p (psf) - CASE A
Roof Slope = 26.56 degrees
Area 1 Area 2 Area 3 Area 4 Area 1E Area 2E Area 3E Area 4E
22.42 -8.70 -19.25 -17.53 27.85 -11.55 -23.52 -21.99
p (psf) - CASE B
Roof Slope = 26.56 degrees
Area 1 Area 2 Area 3 Area 4 Area 5 Area 6 Area 1E Area 2E Area 3E Area 4E Area 5E Area 6E
-19.35 -26.72 -16.89 -19.35 17.81 -14.43 -20.27 -38.39 -21.80 -20.27 24.26 -18.73
The above are based on corner length as follows:
0.4 x Building Height = 12.00 ft (height = 30.00 ft)
0.1 x min. Width = 2.40 ft
Not less than 3’ =
3.00 ft
a =
3.00 ft
Corner Length = 2a = 6.00 ft