Prestressed concrete is to make up for the phenomenon of premature cracks in concrete. Before the use (loading) of components, a pre pressure is given to the concrete in advance, that is, in the tensile area of concrete, the method of artificial force is used to tension the reinforcement, and the retraction force of reinforcement is used to pre stress the tensile area of concrete. When the member bears the tension produced by the external load, the stored preload first offsets the preload in the concrete in the tension area, and then the concrete is tensioned with the increase of the load, which limits the elongation of the concrete and delays or does not cause cracks, which is called prestressed concrete.
This kind of compression is produced by the tension of high strength "tendon" located in or near the concrete, and its purpose is to improve the performance of the concrete in use. Tendons can be composed of single, multi strand or threaded bars made of the most commonly used high-strength steel. The essence of carbon fiber or aramid fiber prestressed concrete is that once the initial compression is applied, the resulting material has the characteristics of high-strength concrete when it bears any subsequent compression force, and ductile high-strength steel when it bears the tension. Compared with traditional reinforced concrete, this can improve the bearing capacity and / or service performance of the structure in many cases. In prestressed concrete members, the internal stress is introduced in a planned way to offset the stress generated by the superimposed load to the required degree.
Prestressed concrete is widely used in buildings and civil structures. Compared with ordinary reinforced concrete, its performance improvement can allow longer span, reduce structure thickness and save materials. Typical applications include high-rise buildings, residential floors, foundation systems, bridge and dam structures, silos and tanks, industrial pavements and nuclear containment structures.
The longer span increases the accessibilit ofground space and parking facilities. For high-rise buildings, thin slab is very important, because at the same cost, it can build more slab than the traditional thicker slab. Due to the large span, compared with the traditional reinforced concrete structure, less nodes are needed. Due to the small number of joints, maintenance costs will also be reduced during the design life, as joints are the main weakness of concrete buildings.
Long term durability.
Better completion of placed concrete.
It requires less building materials.
Its stress resistance is higher than that of ordinary RCC structure, and there is no crack.
It needs high-strength concrete and high-strength steel wire.
The main disadvantage is that the construction requires additional special equipment, such as jacks, anchors, etc.
It requires highly skilled workers under skilled supervision.
The construction cost is slightly higher than that of RCC structure.