Understanding Duration Of Load Of 1 6 For Roof

Load limits on the roof of a building.

Understanding duration of load of 1 6 for roof.

The load factors are all greater than 1 0 since we want to compare the result to the ultimate. Don t worry about the calculations. Where l r shall not be less than 12 psf and not more than 20 psf. The factor for dead load 1 2 is lower than the factor for live load 1 6 because dead load is more predictable than live load.

Factor is equivalent to the earlier use of a 1 3 wind load factor in that the newer wind load provisions of asce 7 98 include separate consideration of wind directionality by adjusting wind loads by an explicit wind directionality factor kd of 0 85. How long will the members be loaded. Tables automatically handle this adjustment. See figure 1 headers.

Since the wind load factor of 1 3 included this effect it must be adjusted to 1 5 in. So consider a simple gable roof on a 24 foot wide ranch framed with 2 6 exterior walls and a 1 1 2 ridge. Here each square foot of roof system delivers 50 pounds of live load and 15 pounds of dead load 65 psf total to the structural support system. Full time loading floor joists serves as the benchmark value.

This is the horizontal distance from the inside surface of the supporting wall to the inside surface of the ridge board. Roofs are under a lot of pressure. R 1 1 for a t less than or equal to 200 psf r 1 1 2 0 001 a t for between 200 psf and 600 psf. Anything hung from or attached to the structural framing is a collateral dead load.

It shall be unlawful to remove or deface such notices. Using lrfd lc 2 the combined design load equals 1 2 times the dead load plus 1 6 times the live load or 15 6 kips. Rather the span is based on the rafter s horizontal projection. Roof live load reduction.

R 1 0 6 for a t greater than or equal to 600 psf. Benchmark values are multiplied by 1 15 to yield snow load values and by 1 25 for 7 day loading. The span would be 11 5 3 4. L r l o r 1 r 2.

In order to stay intact and in place a roof must be able to resist loads both permanent and temporary that are pushing. All loads are listed as pounds per square foot of horizontal projection footprint area. Greater than 10 years 0 9 permanent 10 years 1 0 normal floor ll 1 year 1 075 long term temporary load 2 months 1 15 snow load 7 days 1 25 roof live load 10 minutes 1 6 wind or seismic load less than 2 seconds 2 0 impact load e g. Roof live load may be reduced by the following equation.