Beam post-tensioning. With post-tensioned beams, we suggest the use of the C range system, because of the following characteristics: use of 13mm and 15mm. Freyssinet’s technical services design anchors, jacks and installation equipment, and also post-tensioning kits for prestressing of structures). ETA and CE. Freyssinet group has been active in the Middle east region since the early s, We supply and provide a comprehensive post tensioning system including.
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High tension steel wires of diameter varying from 5 mm to 8 mm about 12 numbers are properly arranged to form a group into a cable with a spiral spring inside. Once the concrete tensionint then the wires are cut or released. The applications tensioniny such type of methods are different.
In the earlier days, pre-tensioning system was mostly used but nowadays the post tensioning system is used. The following ways to do it: Depending upon the situation and structural members the prestressing systems are appropriately decided and used. While for larger span the pre-tensioning system is found to be uneconomical. Among the post-tesnionig system, Freyssinet stem is introduced firstly of all other systems.
Therefore the prestressing force should be measured.
The sides of ducts may obstruct the stretching of the reinforcement at the end remote from the jack arrangement while this part may not receive the full tension if properly not carried out. By this method, the prestress is transferred to the concrete structure as there is bond between the tendons and concrete.
Then the concrete is poured so that many structural elements can be produced in a single line and for that, the shuttering should be provided. L standard system, Lee-Mccall system, electrical prestressing and chemical prestressing.
Also in one line, the remaining wires will be cut off. This thing is properly enclosed in the thin metal steel. The anchorage system consists of a cylinder of good quality concrete and is provided with some corrugations on outside parts.
This has a central hole and is provided with heavy circumferential reinforcement. Such type of method consists of stretching the wires at greater distance apart.
This arrangement will give an additional restraint against the problem of slipping of the tendons.
The numbers poxt systems are available which are patented for the linear prestressing and with modifications to circular prestressing also.
Also, the other systems behave like the above principles and more specifically it is used for the precast beams. In the case of pre-tensioning method prestress, there is a compressive force in the concrete which is because of the bond between the concrete and tenxioning wires and that is kept stretched between the buttresses.
At the end of the member, the excessive bearing stresses are produced because of the anchoring devices which bear against the cracks. In other cases, there is the possibility of extension in some other part of the tendons which are overstressed.
The method of prestressing involves pre-tensioning and post-tensioning methods only in the practical cases. When the tendons are pulled and tightened with the help of jack arrangement against the end of concrete element then the required prestressing force tensikning obtained suitably.
This is the way to put space between the wires which will be filled with cement grout. The different wedging devices and arrangement of wires are available in the different systems. Once the wires are stretched then they are anchored in the stretched positions against the end of concrete member with the help tensloning wedging device.
The economical length of the concrete member should is up to 20 m if such type of prestressing is adopted.
Freyssinet – Silo post-tensioning
If the limited sizes of the concrete are to be produced as mass-production then this method is adopted economically. From the above systems, it is clear that the systems tensoning pre-tensioning prestressing are different from the system used for the post-tensioning systems.
The central hole passing axially through the plug will permit cement grout injected in it. When the curved cable is provided them the above-mentioned defects may be produced. It is very necessary to measure the load applied with the help of jack arrangement and the extension of tesioning so that the proper prestress in the reinforcement will be ensured.
There is considerable difficulty occurs in the transporting of concrete members of longer than 20 m length. These cylinders are then kept in proper position pots then the conical plugs are being pushed into the conical holes after cables are properly tightened.