This method is used in factories and workshops for the production of concrete parts to make these types of prefabricated products.
One of the most widely used construction materials is prestressed concrete, which has been used on a large scale since almost 50 years ago. To make this concrete, the prestressing method is used, during which the concrete is strengthened and its weakness against tension is eliminated. Normally, the prestressing force is applied on the prestressed concrete in two ways. Pre-tension and post-tension are done differently. This means that the steel tension operation, which is in the form of cable or wire, is done before concreting or after concreting.
What are prestressed concrete and post-stressed concrete?
In the method of pre-tensioning, two methods of pre-tension and post-tension are used to create pressure on the concrete structure, which has caused the creation of two types of concrete as follows:
Retracted or prestressed concrete
In this method, the cables, which are inside the protective sheaths, are placed in the desired part, after The concreting operation is done and after the concrete has gained the necessary compressive strength, the cables are pulled. is used
Pre-stressed or pre-stretched concrete
In this method, unlike the withdrawal method, concreting is done after the cables are stretched. In this way, at first the steel, which is in the form of cable or wire, is placed on a pre-made bed. After that, the cables are stretched between the two ends until they flow, and the concreting operation is carried out. After the necessary adhesion between the steel and concrete is established and the concrete gains the necessary resistance, the cables are cut so that the tensile force of the steel is transferred to the concrete structure in the form of compression.
What are the characteristics of prestressed concrete?
Prestressing refers to methods during which an initial, fixed, permanent and permanent stress (Prestress) is introduced to the concrete structure or member. As a result of this primary stress, some of the dead and live stresses in the concrete structure are neutralized. As a result of this, the bearing strength of prestressed concrete increases.
In general, the purpose and main feature of prestressing in a concrete structure is to reduce tensile stresses and limit cracks caused by anchor anchors, due to The loading is on the concrete structure. Because although concrete has high resistance to pressure, it does not have much resistance to tension. For this reason, by creating pressure on the concrete, the tension created in the concrete structure is reduced. As a result, its resistance increases.
What are the advantages of prestressed concrete?
This type of concrete has many advantages over other concretes, including the following:
Flexibility
Flexibility can be considered as the first advantage of prestressed concrete. In this way, it is possible to make the concrete structure flexible by changing some of the pre-tensioning force. Absence of concrete cracks and creep is one of the most important advantages of the structure. of prestressed concrete, it can be pointed out that there are no permanent cracks in it, which increases the durability and longevity of these concrete structures. br>Since when using concrete, the strength of the entire cross section is fully used, the amount of concrete consumption is reduced. In addition, the steels used in this type of concrete have very high resistance, which reduces the need to use steel. As a result, the weight of the structure is reduced.
Application of prestressed concrete
Among the types of concrete in architecture, these types of concrete are mostly used for building bridges, floors, beams, roofs, water sources, and highways, and they are generally not used for building walls and columns. . But in some cases, prestressed concrete is used as an economical way to build structures that are affected by the blast, such as retaining or load-bearing walls, slabs, columns, and beams. In addition, ordinary reinforced concretes can be used in executive spans of approximately 6 meters, which have acceptable performance and are economically viable. But when the executive span is greater than 9 meters, pre-stressed concrete should be used to be more economically compatible with the project.