Correct Answer - Option 3 : Hoyer system
Explanation:
Hoyer system or long line method:
- It is often adopted in pre-tensioning large-scale production.
- In this Two bulkheads or abutments independently anchored to the ground are provided several meters apart, say, 100m. wires are stretched between the bulkheads. MouldsMoulds are placed enclosing the wires. The concrete is now poured so that several beams can be produced in one line.
Magnel-blaton system:
- It consists of a cable of rectangular section is provided, which contains layers of wires 5 mm to 8 mm diameter.
- The wires are arranged with four wires per layer (up to sixteen layers deep for a cable of sixty-four wires).
- The wires in the same layer and the wires in adjacent layers are separated with a clearance of 4 mm. the geometric pattern of the wires is maintained in the same form throughout the length of the cable by providing grills or spacers at regular intervals.
- The grills do not offer any appreciable frictional resistance to the wires which can be moved relative to each other during the tensioning process.
P.S.C Monowire system:
- In this system also the wires are tensioned individually. The anchorages consist of a single piece collet sleeve wedging in a conical hole
- A steel truncated guide leads each wire from the cable to the anchorage point along a gentle curvature. In addition to the guide, a central block is also provided to anchor the central wires.
Gifford - Udall system:
This is the earliest method in this method the wires are stressed and anchored one by one in a separate cylinder using small wedging grips called udall grips. Each grip consists of two half cones. The bearing plate bears against a thrust ring which is cast into the concrete. The duct end is encircled by a helix. Anchorages are supplied to suit the cables of 2, 4, 6, and 12 wires.
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System(country)
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Type of tendon
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Range of force
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Arrangement of tendons
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Type of anchorage
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Freyssinet (France)
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Wires and stands
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Medium-large
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Annular, spaced by helical wire core
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Concrete wedge
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Lee-mc-call (Great Britain)
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Bar threaded at ends
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Small medium large
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Single bars
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High strength nut
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Gifford udall ( Great Britain )
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Wires
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Small and medium
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Evenly spaced by perforated spacers
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Split conical wedge
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Magnel blaton (Belgium)
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Wires
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Small, medium, large
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Horizontal rows of 4 wires spaced bt metal griller
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Flat steel wedge in sandwich plate
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