What are prestressed reinforced concrete structures: advantages and disadvantages

The strength and longevity of concrete structures can be increased with the use of prestressed reinforced concrete. Engineers can improve the performance of concrete in a variety of applications, such as buildings and bridges, by introducing internal stresses to the material before it bears loads.

With this method, pressure is applied to the concrete using steel cables or rods of exceptional strength. As a result, the structure is more durable and less prone to cracking than conventional concrete. Even though prestressed reinforced concrete has many advantages, it’s important to consider any potential disadvantages.

We will examine the benefits and drawbacks of prestressed reinforced concrete in this post. You can decide if this construction method is right for your next project by being aware of these factors.

Definition

Prestressed reinforced concrete structures are construction materials where the concrete is initially subjected to the computed compressive stress during manufacturing. Tensile stress is preformed in the steel reinforcement during the material’s production, which is distinguished by its high strength. In places where concrete will be stressed during operation, it is used to compress the material.

Because the reinforcement is attached to the material and has an anchor fastening at the end, it does not slip during compression. Because the composition of reinforced concrete is reinforced, you can balance the stress. The building material’s service life is increased if it is subjected to useful loads while in use because this prevents cracks from forming.

Prestressed reinforced concrete constructions apply internal stresses prior to external loads in order to increase strength and durability. Significant benefits from this technique include lower material consumption and increased load-bearing capacity, which improve the effectiveness and economy of structures. But there are disadvantages as well, such as greater upfront costs and the requirement for exact building techniques. Making educated decisions regarding the use of prestressed concrete in different building projects is facilitated by being aware of these advantages and restrictions.

Advantages

Prestressed concrete is superior to comparable materials in the following ways:

  • Reinforced concrete beams work well in compression and deflection relative to the center of gravity. They are characterized by a high level of strength along the entire length, which makes it possible to increase the length of spans. This ensures a reduction in the cross-sectional dimensions, as well as a reduction in the weight and size of components.
  • Concrete is a chemically neutral material, which eliminates the possibility of corrosion and deformation of reinforcement.
  • Reinforcement compresses the concrete of assembly units, which eliminates adhesion resistance and reduces metal consumption at the joint.
  • Reinforced concrete structures can consist of joined parts and have the same cross-section, which ensures resistance to external loads. The structures are characterized by increased endurance, which is ensured by compensation for repeated dynamic effects.
  • Prism strength allows for damping changes in reinforcement and concrete that occur with fluctuations in external load.
  • When using building materials, the possibility of concrete and reinforcement deformations is eliminated, which guarantees increased seismic resistance of the building.

Pre-stressed construction is secure. It does not collapse because of the extreme deflection, which indicates the end of strength.

Disadvantages

Specialized equipment must be used to guarantee pre-stressing of reinforced concrete structures. Goods need to be transported properly, stored carefully, and installed by professionals. Even before it operates, this won’t result in an emergency situation with the building material.

Production necessitates precise pre-stressed reinforced concrete structure calculations, which are completed by highly skilled experts. The reinforced concrete structure under construction may completely collapse due to errors in production and design calculations.

Cracks caused by longitudinal tensile stress will lower the load-bearing capacity.

Metal-intensive formwork is required to guarantee axial tensile strength. Steel consumption rises as a result.

It is essential to use compensating materials to ensure heat and sound conductivity. These kinds of structures have a lower threshold for fire resistance.

It is clear from the nature of prestressed reinforced concrete that acids, salts, and other chemicals cannot be tolerated by it. In this instance, both the products’ destruction and their ability to support loads are reduced. Their striking weight is a drawback of the design.

Materials for structures

One type of multi-component building material is reinforced concrete. Concrete and steel reinforcement make up its composition. The quality parameters of the materials are established during the design of reinforced concrete in compliance with GOST standards.

Concrete

In order to guarantee the prestressing and resistance of concrete, only dense mixtures weighing between 220 and 2500 kg per square meter are utilized.

The material can be prestressed by infusing the mixture for a minimum of 28 days. A partial loss of stressed quality by concrete may be seen during the first stages of operation; this is explained by a reduction in the stress of steel elements. A reinforced concrete element’s normal cross-section is determined in compliance with the design and specifications needed for continued operation.

Reinforcement

For the duration of its service life, steel reinforcement needs to be stressed and resistant to stretching. Because it can withstand loads for an extended period of time, concrete cracks are unlikely to occur. Low yield, high-strength steel is used to make construction materials. Steel design features have to be completely compliant with concrete creep.

During production, a value slightly higher than that specified in the design documentation and requirements for the finished material is set in order to compensate for the operational loss of a specific amount of prestress.

Reinforcing wire is used in the construction of reinforced concrete structures:

Cold-formed, hot-rolled, hardened reinforcement, welded frames, and ropes are used in the construction of reinforced concrete structures. The dimensions of the final reinforced concrete product directly affect the cross-sectional area of the reinforcement. The cross sections of wires and ropes are ring- and sickle-shaped, with smooth, periodic reinforcement. Steel needs to be transversely forceful enough. There should be a 0.2 percent metal flow in relation to elongation.

According to the stretched fiber’s specifications, the reinforcement’s strength class ought to be 0.95 or higher. It ought to possess plasticity and cold resistance. By creating a complex spatial surface, the prestressed reinforcement’s optimal force is guaranteed. The material needs to be weldable for this reason.

During production, the tension of the reinforcement is guaranteed through mechanical or electrothermal techniques. In the first instance, levers, jacks, and weights are used to accomplish this. Anchors must be positioned at the ends of rods that have been prepared to the necessary length for the electrothermal method. They elongate as a result of being heated to 400 degrees. The reinforcement is fastened to the supports in this state. The appearance of stress results from the anchors preventing the rods from shortening during cooling.

Area of use of structures

When using traditional reinforced concrete is not appropriate, prestressed structures should be used instead. When load-bearing strength is needed, they are perfect. Prestressed reinforced concrete structures are used in a variety of construction domains, including hydraulic, special, civil, and industrial engineering.

Bridges with large spans are constructed using reinforced concrete structures. It is advised that they be used when building dams and pressure pipelines. It is installed with waterproof containers made of reinforced concrete products.

The structures are frequently used to make enclosing panels and retaining walls. Reinforced concrete structures are used whenever a foundation or set of stairs needs to be constructed. They are employed when building structures in seismic and explosive zones. Products made of reinforced concrete are used to create prefabricated monolithic structures. They entail using reinforcement to join individual prestressed precast elements. Power transmission line poles and columns are constructed with reinforced concrete. They are used to create tunnel frames.

Advantages Disadvantages
Improved load-bearing capacity: Prestressed concrete structures can support greater loads compared to traditional concrete. Higher cost: The materials and techniques for prestressing can be more expensive.
Reduced material usage: By using prestressing, less concrete and steel are needed, which can be more efficient. Complex construction: The process of prestressing requires careful handling and expertise, making construction more complex.
Increased span lengths: Prestressed concrete allows for longer spans without additional supports. Maintenance: While durable, prestressed concrete may still require maintenance to address issues like cracking.

Prestressed reinforced concrete constructions have increased strength and durability, among other important advantages. Compared to conventional concrete, these structures can support larger loads and span longer distances thanks to the application of pre- or post-tensioning to the reinforcement. This makes them perfect for big projects where extra strength is required, like high-rise buildings and bridges.

Prestressed concrete does have certain disadvantages, though. Budget-conscious projects may be concerned about the upfront costs associated with materials and installation, as they may be higher than those associated with conventional concrete. The intricacy of the building process also necessitates specific knowledge and tools, which raises the total cost even more.

In conclusion, even though prestressed reinforced concrete structures have many benefits in terms of functionality and performance, it is crucial to balance these benefits against the increased expenses and technical requirements. The appropriate assessment of project specifications and financial limitations will assist in deciding whether this cutting-edge concrete technology is the best option for your building requirements.

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Dmitry Sokolov

Chief engineer in a large construction company. I have extensive experience in managing construction projects and implementing modern technologies.

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