2308.7.5 Wind Uplift
The roof construction shall have rafter and truss ties to the wall below. Resultant uplift loads shall be transferred to the foundation using a continuous load path. The rafter or truss to wall connection shall comply with Tables 2304.10.1 and 2308.7.5.
REQUIRED RATING OF APPROVED UPLIFT CONNECTORS (pounds)a, b, c, e, f, g, h
|NOMINAL DESIGN WIND|
|ROOF SPAN (feet)||OVERHANGS |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 1.61 km/hr, 1 pound = 0.454 Kg, 1 pound/foot = 14.5939 N/m.
Mean Roof Height (feet) EXPOSURE 15 20 25 30 35 40 45 50 55 60 B 1.00 1.00 1.00 1.00 1.05 1.09 1.12 1.16 1.19 1.22 C 1.21 1.29 1.35 1.40 1.45 1.49 1.53 1.56 1.59 1.62 D 1.47 1.55 1.61 1.66 1.70 1.74 1.78 1.81 1.84 1.87
- The uplift connection requirements are based on the framing being spaced 24 inches on center. Multiply by 0.67 for framing spaced 16 inches on center and multiply by 0.5 for framing spaced 12 inches on center.
- The uplift connection requirements include an allowance for 10 pounds of dead load.
- The uplift connection requirements do not account for the effects of overhangs. The magnitude of the loads shall be increased by adding the overhang loads found in the table. The overhang loads are based on framing spaced 24 inches on center. The overhang loads given shall be multiplied by the overhang projection and added to the roof uplift value in the table.
- The uplift connection requirements are based on wind loading on end zones as defined in Figure 28.5-1 of ASCE 7. Connection loads for connections located a distance of 20 percent of the least horizontal dimension of the building from the corner of the building are permitted to be reduced by multiplying the table connection value by 0.7 and multiplying the overhang load by 0.8.
- For wall-to-wall and wall-to-foundation connections, the capacity of the uplift connector is permitted to be reduced by 100 pounds for each full wall above. (For example, if a 500-pound rated connector is used on the roof framing, a 400-pound rated connector is permitted at the next floor level down).
- Interpolation is permitted for intermediate values of Vasd and roof spans.
- The rated capacity of approved tie-down devices is permitted to include up to a 60-percent increase for wind effects where allowed by material specifications.
- Vasd shall be determined in accordance with Section 1609.3.1.