Roof Tributary Load

Tributary areas for gravity loads.

Roof tributary load.

It is necessary to remember that gable trusses with outlookers having an overhang of more than 1 ft will be under loaded if designed to support the load generated by a tributary area equal to 2 ft of roof load only. A fixed node will provide support in both directions down the length of the roof truss members often called the x and y directions. If the load is 100 psf the load to the beam would be 12 ft x 100 psf 1200 plf. Notice that the middle tributary zone must carry more weight than the adjacent areas b and d.

D dead load l live load l r roof live load w wind load e earthquake load s snow load r rain load f flood load t temperature or self strain load h hydrostatic pressure load design of a member or of a segment of a member must be based on the load case that produces the largest force stress displacement value. The left wall has 7 ft of tributary width and would receive a load of. Load calculation for each tributary area a 40sqft x 50psf or 2000 lbs b 19 5sqft x 50 psf or 975 lbs c 21 sqft x 50 psf or 1050 lbs d 19 5sqft x 50 psf or 975 lbs. E tributary width tributary loading or tributary width is the accumulation of loads that are directed toward a particular structural member.

In order for a roof truss load to be stable you need to assign two of your nodes on each truss to be support nodes. It goes without saying that in a warmer climate the snow load probably would be less so you need to check your code book for live loads and dead loads in your region. Our sample homes are in an area where the snow load is 50 pounds per square foot of roof area treat snow as live load. It can also be called the load periphery.

The area from the center between two beams to the center of the next two beams for the full span is the load on the center beam. Loads uniformly distributed over an area of roof or floor are assigned to individual members rafters joists beams girders based on the concept of tributary area. The tributary area times the pressure on the surface. If the load is 100 psf the load to the beam would be 12 ft x 100 psf 1200 plf.

This means that one is a fixed node and the other is a rolling node. The tributary area is a loaded area that contributes to the load on the member supporting that area ex. An outlooker can be defined as a framing member that supports the portion of the roof beyond the face of a gable end truss. Tributary width is 7 ft 5 ft 12 ft.

The tributary load on the member is found by concentrating or. Tributary width is 7 ft 5 ft 12 ft. 11 04 2014 if the beam is supporting a floor roof or wall that has a pressure loading normal to the surface the total force on the beam equals the area of surface supported i e.