Reinforced concrete trusses: rafter, reinforced concrete, concrete (24 m, 18 m) – scope of application

Modern construction requires reinforced concrete trusses, which are renowned for their strength and longevity. Large spans, like those found in warehouses, factories, and other industrial buildings, require structural support, which is provided by reinforced concrete trusses, rafter construction, or concrete.

These trusses are available in a range of sizes, with 24- and 18-meter spans being the most popular. The particular requirements of the building and the weight it must support determine the span length and truss type to use. Every variety of truss has distinct benefits and is employed in various situations to guarantee maximum efficiency and security.

It is essential for engineers, builders, and architects to comprehend the range of applications for these trusses. It assists in choosing the appropriate truss type for the project, guaranteeing that the structure is both reasonably priced and able to withstand the demands made of it.

What are trusses

A reinforced concrete truss is a unique construction consisting of interconnected steel reinforcement rods embedded in concrete, intended for roof installation and serving as a framework for an attached structure.

The upper chord refers to the rods at the top, and the lower chord refers to the rods at the bottom. Racks are structural components that are situated in a vertical plane.

Diagonal elements are pieces that are positioned at specific angles. The racks and bracing components collectively make up the structure’s lattice. Reinforced concrete beam nodes are the intersections of braced blocks and vertically oriented posts.

• High level of strength and reliability of the entire building
• The reinforced concrete frame creates a rigid structure and guarantees the ability to withstand heavy loads for many years
• Concrete and steel are not afraid of adverse chemical and climatic influences, do not change their characteristics under ultraviolet radiation, rain, frost, etc.d.
• The rafter element fully complies with the most stringent requirements of fire safety standards

With the use of contemporary machinery, manufacturers can produce reinforced concrete trusses quickly and strictly adhering to legal specifications. A structure with an 18-meter span weighs more than 7 tons, and one with a 24-meter span weighs roughly 12.3 tons. Trusses can therefore only be installed with specialized tools.

1. A monolithic element with an integral structure, which is created only in factory conditions.
2. Composite structure – includes several parts that are assembled directly on site.

Main types of trusses

Rafter and sub-rafter trusses are the two types of trusses used in modern construction. When working with trusses, the design phase is thought to be the most crucial since accurate calculations guarantee both the structure’s ability to support the specified loads and the quality of installation; however, incorrect design calculations frequently result in building collapses.

Rafter structures

The most complicated option is the reinforced concrete rafter truss. More commonly found rafter structures made of metal or timber (wood) are also available on the market. Structures made of reinforced concrete are often only utilized when alternative materials are unsuitable because they lack the necessary properties and indicators for stability and protection.

The primary factor for wooden rafter structures is the area intended for the object’s placement. It is crucial to accurately calculate the area and ascertain the stability of the trusses in order to guarantee the strength and rigidity of the structure and to remove the possibility of it collapsing under its own weight. Wooden trusses must be securely fastened; experts are typically called in to handle this chore so you don’t have to take the chance of doing it yourself.

When compared to alternative options, reinforced concrete trusses are the most dependable and long-lasting. Due to their enormous weight, they are only utilized in a very limited number of places, such as large structures, climatically specific areas, industrial buildings, etc.

Rafter structures

Not as frequently as rafters are these structures used. As long as the columns’ dimensions are greater than those of the supporting structure, they are relevant when building attics. In this instance, the purlin beam, which ranges in length from 12 to 24 meters, serves as the truss’s foundation.

Because of the bundle-shaped reinforcement used in the construction of these trusses, the overall structure’s reliability is increased and weight is considerably reduced. Using specific tools, trusses are installed directly on rafter-style columns. The welded joints on metal and reinforced concrete structures will require additional equipment.

When a building has transverse load-bearing walls or all of the walls are transverse, these truss types are used. Attic roof construction can only employ purlin beams. When the racks are placed directly beneath the feet, or columns, the structure is under minimal pressure to maintain maximum stability and dependability.

Dimensions of reinforced concrete trusses

Concrete and reinforced concrete products are manufactured in compliance with the national GOSTs. Trusses made of reinforced concrete are not an exception, of course. The primary dimensions of the elements are established, and marking is done in compliance with the standards that have been set.

• Diagonal – length from 18 to 24 meters, height from 2.6 to 3.2 meters, width from 0.2 to 0.3 meters.
• Non-diagonal – length 18-24 meters, height 2.6-3.2 meters, width 0.2-0.3 meters.
• Triangular non-diagonal – length from 2 meters, height 1.2-2.7 meters, width 0.2-0.25 meters.
• For pitched roofing – from 1 meter long, height 2.2 meters, width 0.5 meters.
• For tiled roofing – with a length of 1 meter, height 3.3 meters, width 0.5 meters.

The most popular sizes are 24, 36, and 18 meters. According to GOST, an element’s maximum allowable weight is between 6 and 50 tons. You can find reinforced concrete trusses of any size and specification in Moscow and the surrounding areas.

Nearly all of the essential truss attributes and characteristics—including dimensions, type, design features, and properties—are provided by the marking. The marking consists of multiple sets of letters and numbers that can be interpreted using GOST 23009.

• 1 group of values ​​- size number, product type, length (rounded to meters).
• 2 group of values ​​- numerical index of bearing capacity, indicates the class of reinforcement (if it is pre-stressed), type of concrete (indicated only for products made of lightweight concrete).
• 3 group of values ​​- not always present, indicates resistance to seismic shocks, aggressive environments, indicates the presence of embedded parts, additional holes, etc.d.

Example of decoding the marking: reinforced concrete truss 3FS, 18 meters long, with a bearing capacity of type 6, prestressed reinforcement A600, filled with lightweight concrete, with embedded parts, is designated as 3FS18-6A600L-1. The sizes and shapes of various reinforced concrete trusses (rafter/sub-rafter), as a rule, are indicated in special tables.

Scope

Like structures made of other materials, reinforced concrete trusses are employed in the construction of a variety of objects, including hydraulic gates, bridge spans, roof installations on various kinds of structures, and supports for power transmission lines.

Trusses are useful in a variety of buildings because of their many beneficial qualities, which include protection from cracks, resistance to frost and aggressive influences, strength and reliability, durability, and high load-bearing capacity. They can be used to create intermediate supports for the installation of later structures, as well as to support columns, roofs, and cover spans.

Trusses are occasionally utilized in open form for the construction of industrial sites and buildings. Trusses made of reinforced concrete are never used in residential construction.

For large structures and long spans (e.g., 24 and 18 meters), reinforced concrete trusses with specific rafter and concrete designs are essential. They are perfect for a variety of applications, from bridges to large industrial buildings, because of their strength and versatility. Knowing their scope makes it easier to select the best kind for each unique project, guaranteeing efficiency and durability.

Classification of reinforced concrete trusses

Reinforced concrete trusses can be polygonal, non-diagonal (they can also be arched), or diagonal depending on the shape of the structure. One classification that is frequently brought up is typical, diagonal/non-diagonal. There are many common options available here; everything is dependent upon the number of floors and span sizes.

• A non-diagonal truss is used in cases where the roof has a small slope. This type of truss is also relevant for a building with communication systems, the step is 6/12 meters.
• Objects without heating, with a roof made of asbestos-cement sheets, suggest the use of non-diagonal trusses, with a span of 9/18 meters.
• Segmental non-diagonal and diagonal trusses are always used to create pitched roofs.

The most crucial factors considered when building trusses are the following: the materials’ response to high and low temperatures, the mixture’s concrete’s strength and density, the steel grade, and the materials’ reaction to corrosion. Because the structures cannot be installed independently and the elements’ weight is too great for any low-rise building to support, they are not used in private residences.

• The total weight of the system includes the weight of the rafter truss and roof covering.
• The main loads include: strong wind, precipitation, snow. There are also periodic ones – earthquakes and other force majeure circumstances.
• The truss frame includes a lot of reinforced steel elements, which ensures maximum stability.
• In order to reduce the weight of the product, lightweight concrete can be used, which does not affect the quality in any way.
• Before pouring, the steel reinforcement is covered with special impregnations that eliminate early corrosion, which makes the roof resistant to moisture, snow, frost, ultraviolet radiation, temperature changes.
• The truss outline includes two chords to form a strong bend, and the lattice consists of braces and posts.
• Trusses can be polygonal and segmental, they all differ in slope and shape of the belt.

For a wide range of construction applications, including large industrial structures and residential buildings, reinforced concrete trusses provide an adaptable solution. Their capacity to span large distances—up to 24 or 18 meters—makes them perfect for uses where dependable, strong support is essential.

Because they are made with both steel and concrete reinforcements, these trusses are especially strong and long-lasting. They are a common option in contemporary construction because of their superior resistance to tensile and compressive stresses.

Reinforced concrete trusses improve the stability and lifespan of buildings when they are used as rafter trusses in roofs or in other structural capacities. Their wide range of applications reflects how crucial they are to a variety of engineering and architectural projects.

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