Prestressed concrete beam is one of the modern materials in the construction industry with unique features such as the ability to be used in taller spans compared to other concrete ceilings and speeding up construction operations.

Alongside other advantages that we will become more familiar with later, this feature has led to an increasing use of these precast components, gradually replacing common types of beams in construction such as block beams.

What is Prestressed Concrete Beam?

Concrete is a material that is very resistant to compressive stresses but very weak in tension. If a concrete member with a compressive strength of 35 megapascals is subjected to tensile stress, when the average stress in the concrete reaches about 2 to 3 megapascals, the concrete cracks. In addition to its low tensile strength, the behavior of concrete in tension is unpredictable and its failure is sudden.

To eliminate this weakness in concrete, steel reinforcement is used to strengthen the concrete member, ultimately forming reinforced concrete (concrete with steel reinforcement).

The use of reinforced concrete has been accepted and widely used in the construction of various building and industrial structures for years. Although this composite material has many advantages, it also has disadvantages such as increasing the weight of the structure and not utilizing the full load-bearing capacity of concrete.

Therefore, after extensive research conducted in the past century, a new type of concrete called prestressed concrete was invented and produced. Prestressed concrete is a type of reinforced concrete in which steel reinforcements are tensioned using mechanisms, creating pressure in the concrete and allowing for more efficient use of its capacity. Prestressed concrete beams are members composed of prestressed concrete along with high-strength steel. In other words, prestressed beams or precast concrete beams are made in an inverted T-shaped section using high-strength steel wires (1400 to 1900 newtons per square millimeter) and concrete with a minimum compressive strength of 35 megapascals.

Stages of Prestressed Concrete Beam Production

Now that we are familiar with the initial features of prestressed concrete beams, it is necessary to see how these materials are made and what stages need to be completed in the construction and implementation of prestressed beams. Then, we will discuss the advantages, disadvantages, and limitations of using them as one of the common types of beams in the construction industry. It should be noted that to produce prestressed beams, specific technology and production lines with special features are required, along with engineers and experienced individuals in this field who have particular capabilities. In the previous part of the article, we became acquainted with the specifications that prestressed beams need, such as concrete strength and the required prestressing level in the prestressing cables.

What Are the Types of Prestressed Beams?

These rings are designed for ease of transportation and also prestressed beams with hooks are installed on the main beam using hooks during installation and do not require anchoring.

Introduction to Prestressed Hooked Beams

Appearance of Prestressed Beams

The surface of prestressed beams is not smooth, and these beams have a T-shaped cross-section. If you want to know how many rebars are used in these beams, you just need to look at the beginning or end of the beam.

What Are the Sizes of Prestressed Beams?

In addition to high strength and durability, another important feature of these beams is their length. These beams are made in sizes ranging from 1 to 12 meters, and the weight and volume of these beams are less than traditional beams. Ultimately, the suitable strength and light weight of these beams have made buildings using them more resistant to hazards such as earthquakes.

The weight of prestressed beams should be greater than or equal to 28 kilograms per meter in the standard state. It should be noted that the reason for the higher weight of prestressed beams compared to other beams is that prestressed beams are entirely made of concrete in their section.

Sometimes there is a misconception that prestressed beams make the ceiling heavier; however, this perspective is completely wrong, and in fact, prestressed beams contribute to lightening the ceiling. Calculations have shown that if prestressed beams are used in a ceiling, the weight of the ceiling decreases by approximately 7 to 9 kilograms per square meter.

Implementation of Prestressed Beams

One-way slab ceilings are made up of a series of secondary beams or prefabricated beams placed close to each other, with a distance of up to 50 to 70 centimeters filled with clay, concrete, or u...

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