Compared with ordinary reinforced concrete, prestressed concrete has superior advantages in saving engineering materials, increasing crack resistance and durability, improving stiffness and reducing deformation, and improving structural fatigue. The details are as follows:

Because prestressed concrete structures can use high-strength prestressing tendons, the strength is no longer constrained by the small ultimate elongation value of concrete, which greatly reduces the steel consumption. If low-alloy steel and cold-drawn low-carbon steel wire or medium-strength steel wire are used as prestressing main bars, the steel can be saved by 20%~50% compared with ordinary reinforced concrete components; if high-strength prestressing main bars are used, the steel can be saved by 60%~70%. At the same time, because prestressed concrete components can reduce the section and be made into thin-walled components, the consumption of concrete can generally be saved by 10%~30%. If prestressed composite slab in-situ structure is used, a large amount of wood can also be saved.

Because prestressing force is applied to the parts of the structural components where the tensile zone may crack, this avoids the cracks that occur in the case of using reinforced concrete. For example, the lower chords of reinforced concrete trusses and water pools, digestion pools, oil tanks, pressure pipes, etc., when prestressed, can enhance the crack resistance and impermeability of the structure.

Because the designed prestressed concrete components do not crack under working loads, the stress tendons in the structure are protected from external harmful factors, thus greatly improving the durability of the components. Structures such as factory buildings and metallurgical plants with corrosive media environments and high-temperature workshops are suitable for using prestressed concrete components.

After the structural components crack, the stiffness decreases rapidly, but the prestressed concrete components can avoid cracks under working loads, which increases the elastic range of the structure, reduces deformation, and relatively improves the stiffness. At the same time, it can also make beams and other components produce a certain counter-arch (that is, upward counter-deflection). Therefore, under working loads, the deflection and deformation of prestressed concrete beams are much smaller than those of similar ordinary reinforced concrete, so it is particularly suitable for large-span structures, large cantilevers and other structures with deformation control requirements.

Because prestressed concrete can use high-strength concrete and high-strength stress tendons and other efficient materials, it can reduce the section of the components, reduce the self-weight of the structure, and can also be made into thin-walled components. Taking a 1.5m×6.0m large roof panel as an example, the height of the main rib of an ordinary reinforced concrete roof panel is 30cm, while the height of the main rib of a prestressed concrete roof panel is only 18~24cm. The thickness of the web of thin-walled components is generally 10~12cm in ordinary reinforced concrete, while it is 6~8cm in prestressed concrete, thus greatly reducing the self-weight of the structure. The self-weight can usually be reduced by about 20%~30%. Due to the reduction of self-weight, large-span, heavy-load, and super-high-rise structures are easier to apply and develop.

Structures and components subjected to repeated dynamic loads, such as crane beams, bridges, or structures with suspended cranes, are often subjected to reciprocating loads, and the structure is in a state of continuous loading and unloading. When this repeated change exceeds a certain number of times, the material will be damaged below the static strength. Due to the initial stress of the prestressing tendons after tensioning, the change in the stress of the prestressing tendons under repeated loads is generally less than 10% of the initial stress, that is, the amplitude of fatigue stress change is small. This small amplitude of stress change will not cause fatigue of the steel. This improves the fatigue resistance of the components.

With the development and application of large-span and thin-walled components, such as thin-walled box-shaped, T-shaped, and I-shaped section components, if ordinary reinforced concrete components are used, under working loads, the thin walls near the supports often produce diagonal cracks due to shear or torsion, thus affecting the widespread use of such components. If some prestressing tendons are arranged in the thin-walled structure, the crack resistance and torsional resistance of the components can be improved, and the appearance of cracks can be delayed, the crack width can be constrained, and the shear resistance can be improved. For vertical structures, the lateral resistance is improved.

In order to prevent large-flexibility compression members from out-of-plane bending after being subjected to a certain pressure and premature instability, a certain prestress can be applied to the concrete compression members. Because the prestressing tendons have been tensioned to establish stress, this improves the crack resistance and bending resistance of the concrete, so that out-of-plane bending is not easy to occur, and the stability of the components is improved, and the compressive strength of large-flexibility components is increased.

Prestressed tendons can also be used to assemble prefabricated components into integral components, such as post-tensioned block beams, prestressed plate columns or beam-column structures, which provide structural development for large-scale prefabricated integral prestressed buildings, bridges, or water pools, oil tanks, etc., allowing prefabricated blocks to be transported to the site for in-situ casting or assembled into an integral structure, thus greatly improving the industrialization and factory-based level of prestressed structures.

(10) A reinforcement method

When the cracks in reinforced concrete structures are too large, prestressing can be applied to reduce or repair cracks, or small-span structures can be changed into large-span structures or added layers by removing columns, and prestressing can be used to improve the bearing capacity.

Because prestressing can reduce the thickness of the structure, the building clearance can be increased, or the number of floors can be increased without changing the clearance, or the total height of the building can be reduced without changing the number of floors.

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