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Unformatted text preview: SOUTHLINE STEEL INDUSTRIES | I www.southlinesteel.com Steel Roof Trusses An Overview on Designing, Manufacturing, and Installing Roof Trusses Most building roofs can be framed with engineered light- gauge steel trusses which are manufactured from C-Shaped metal studs. Prefabricated steel trusses offer a high-strength, light-weight roof system that can be installed quickly. Roofs on more than 20% of all new commercial structures in the United States are built with light-gauge steel trusses. 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. Scissor Truss (shown) provide a dramatic ceiling effect. This truss type will exert lateral forces on walls if not nstalled with a fixed and slide end. A standard truss is a series of triangles - a 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. However, for all the advantages, proper installation tech- niques and bracing are critical. Additionally, trusses should not be modified in the field without consulting the truss manufacturer. Cutting a web member, for example will radi- cally alter its strength. Truss Types There are many truss types. The most common types are shown on the facing page. Most roof trusses have webs that run at an angle between top and bottom chords. One exception is the gable-end truss in which webs run vertically. These trusses sit atop a build- ing’s end walls and are more like a wall than a truss. The gable-end truss must be supported along the entire length, and stabilized at the truss/wall intersection. There are a number of truss types that leave space for attic storage or living area. In any roof truss, however, attic or living space comes at a price. The bottom chord of the attac truss also acts as a floor joist and must be sized to accommodate a live load – typically between 20 and 50 psf. A roof truss with attic storage translates to roughly twice the weight of the same truss span with no attic. For example, a fifty-foot truss designed without attic storage may weigh between 300-350 lbs. A fifty foot truss designed with a 9 foot by 9 foot attic opening may weigh between 600 and 700 lbs. Some truss manufacturers use a proprietary shape for the truss bottom and top chords. A non-proprietary shape truss is any truss made from standard cold-formed steel shapes, usually C-Shaped stud material. The standard and proprie- tary configurations have their advantages and disadvantages, ii | Steel Roof Trusses Southline Steel Industries | (850) 865-5344 and it’s up to the building designer to determine which is the best choice. the best choice....
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This note was uploaded on 04/24/2011 for the course CIVIL ENGI 101 taught by Professor Anasdaradkah during the Spring '11 term at University of Jordan.
- Spring '11