The roof truss is one of the components of house engineering construction. It is mainly used to bear the load of the roof and the structure and does not rely on the internal partition wall to support it. Roof truss plays an important role in building the roof of a building, so we need to understand the components of the roof truss and the importance of choosing materials. The roof truss can have different shapes, such as common triangles, arches, and trapezoids. In addition, we can also build other shapes for roof trusses according to our design.
Roof trusses usually use a triangular structure, which can be divided into an upper chord, bottom chord, vertical web bars, and oblique web bars. Use various elements and components to connect to each other at each node. Thus, the combination of these components forms a stable and rigid triangular structure. If a large-span space is needed, we should use steel trusses or reinforced concrete roof trusses. The wooden roof truss is suitable for use in a space with a smaller span. Since both sides of the triangular roof truss have horizontal compression elements and other horizontal tension elements at the bottom, these two forces act at the same time to counteract each other, so that the triangular roof truss is balanced and can withstand greater vertical loads.
Except for the triangular roof trusses, arched roof trusses are popular recently. The characteristic of the arched roof truss is that it mainly uses curved steel as the top and bottom strings. The arched roof truss not only has a strong supporting capacity but also greatly enhances the beauty of the building design.
From the structural point of view, there is another more common trapezoidal roof truss. The force of the members of the trapezoidal roof truss is better than the triangular truss. When the upper and lower chords of the trapezoidal truss are in parallel, the force of the members is worse than the trapezoid, and the types of web members will be reduced. Most of this type of roof truss is suitable for the construction of bridges.
In construction projects, most of the roof trusses are made of materials such as steel or reinforced concrete. Among them, the steel truss can provide better support function, has high durability, and can withstand higher pressure. If a protective coating is applied to the surface of the steel truss, the service life of the steel truss can be prolonged. Compared with wood trusses, steel trusses are more durable because wood trusses are eroded by termites and cannot effectively withstand fires. Therefore, steel truss is often used to construct large buildings, such as factories, residential areas, and commercial buildings.
Types of Steel Truss
North light truss
The North Light truss mainly uses glass on the slope toward the north to reduce the gain of solar energy. The use of natural lighting reduces the carbon emissions of the building and reduces overheating situations. The structure of the North Light truss is a steel triangle, which is suitable for short-span buildings such as traditional industrial plants and workshops.
The structural feature of the Pratt truss is that the chords will be welded in an ‘N’ design. Pratt truss can be divided into two types, one is when the diagonally placed components will be in tension under gravity load. The other is a vertically placed component for compression. It is suitable for large-span buildings such as bridge construction and aircraft hangars.
The Fink truss is a very common type of truss. Its chords are arranged in a simple, short-distance arrangement and designed with a "W" structure. This type of truss is suitable for building roofs of small houses with small spans.
Warren truss is very similar to Pratt truss. The components are all arranged in the shape of "W" so that they have the same tension and compression. But there are fewer components than Pratt truss. This type of truss can also be used on buildings with a span of up to 100m. It is suitable for the truss of a crane beam.
The design of the scissors truss has two slopes, and its center is the ceiling, which can create a larger space. These special-shaped trusses are mostly used in churches and museums.
King Post Truss
King post truss is one of the trusses with a very simple design. Mainly used for houses or garages with a span less than 8m. There are generally two angled support members.
Queen Post Truss
Compared with the king post truss, the queen post truss can be used in a larger span. It can be used for the construction of 10m roofs and bridges. But this type of truss has been replaced by the fink truss.
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