Roof truss

Roof Truss, types and construction

1. Roof truss Done By: I.Lydia Kings college OF ENGINEERING TANJORE

2. Introduction Residential metal roofing is primarily made of Steel or Aluminum. Copper, zinc and titanium are also used in specialized architectural applications for homes. Steel roofing for residential applications is very lightweight with the heaviest about 1.5 pounds per square foot when installed. The products are initially produced in giant rolls at the steel mills. Most building roofs can be framed with engineered light-gauge steel trusses which are manufactured from C-Shaped metal studs.

3. Prefabricated steel trusses offer a high-strength, light-weight roof system that can be installed quickly. In residential construction, wood trusses still dominate the industry, however light gauge steel roof systems are gaining ground in markets where additional strength is needed, or where greater free spans are required.

4. Truss A standard truss is a sense of triangles : stable geometric shape that is difficult to distort under load. Regardless of its overall size and shape, all the chords and webs of a truss form triangles. These triangles combine to distribute the load across each of the other members, resulting in a light structure that IS stronger than the sum of the strength of its individual components . Some of the Steel roof Trusses generally used are - King post, Queen post, Fink, Howe, Pratt, Warren, Fan and North Light.

5. Roof truss strength derives from the triangle shapes that comprise the truss itself. Triangles are naturally rigid geometric shapes that resist distortion. Top chords are i n compression and push out at the heel and down at the peak. The bottom chord is normally in tension to resist outward thrust. The webs form smaller triangles that strengthen the overall structure and provide rigidity. Loads on the individual webs can be either compression or tension, depending on the type of load.

6. Specifying a Truss Trusses are manufactured from C-Shaped Galvanized steel. The strength of each member derives from its geometry, rather than weight. When specifying a roof system with a truss manufacturer; the builder/developer should include the span of the roof, the pitch, the top-chord overhang, the end cut and soffit return details needed, and any gable-end preferences . Typical stresses in a roof system show some members under compression and others under tension. When Specifying a truss manufacturer, there are a number of items the building designers need to provide. Most truss manufacturers will provide the building designer With a checklist that describes the details needed to initiate a truss design .

7. C-Shaped Galvanized Steel Loads acting on a truss

8. Construction Process As with any structural member, a faulty design will undetermined even the most professional of installations. Your roof truss will need to be able to handle the expected dead loads and live loads on your structure’s roof. The truss will also need to be supported adequately at its ends

9. The roof truss will have a horizontal lower chord, and 2 angled upper chords that follow the roof line. These chords will be connected by web members, which will be oriented to form triangles. Your design should call for the same size lumber for each member.

10. After the truss is been bolted up, it is lifted and placed as per the plan. And this way, one by one, after placing them all, the structure is ready. At last, this is followed by covering the top with the material according to the use.

11. Protection (Metallic Coating) All Steel Roofing has a protective barrier on both sides of the sheet called a metallic coating which protects against rusting, This is underneath and separate from any paint which imparts color to the product. T here are two types of metallic coatings used: Galvanized : This is 100% Zinc in Various thicknesses depending upon the product usage Galvalume or Zincalume : A mixture of aluminium and zinc. (55 percent by volume aluminiu m ) Metallic coatings "sacrifice" themselves to protect the Iron (Fe) in steel from oxidation when exposed to the air and moisture is present.