Truss is basically a triangle or arch shapes frame used a majority in roof cover it.
The Composite Roof truss is defined as a truss whose compressive members are of timber and whose tension members are steel.
The Composite Roof Truss is made of two materials such as timber and steel or wrought iron. Due to Combination of two materials this truss known as the composite roof trusses.
In this roof, the tension members are made from steel and compression member are made from timber. Steel is used as a tension member because its strength resists tensile stresses. Steel is having greater tensile strength than timber. In the framework, the member in tension is usually replaced by a steel rod. The Bottom chord of the truss acts as tie beam and this tie beam receives the ends of the principal rafters and prevents the wall from spreading out due to thrust. The vertical king rod is used to prevent the sagging of tie beam at the centre of a span. King rod is used when there is a need to support the weight of an expansive roof. This tie beam and king post are made of steel.
Principal rafters in composite trusses are made of timber, as the rectangular sections of timber have a great strength in compression and purlins can be fixed easily. Purlins, struts and common rafter are also made from the timber. Covering of roof is made from a different material such as Mangalore tiles, A.C sheets or even pre-coated sheet. The composite truss is light in weight and economical.
If tension members are made from timber than the section of trusses become very heavy. So the steel is used in tension members and reduces the section at joints. The special fittings are required at the junction of steel and timber member. The joints in composite trusses should be such as of cast or forged fittings. In composite roofs, Different types of fittings such as C.I head, C.I shoe, steel angle bolts and straps are used.
The composite roof truss is light in weight and economical. A well-designed composite roof truss thus plays an important role in your safety and save money, too.
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