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123. FREYSSINET C AND K SYSTEMS ANCHORAGES

All Freyssinet anchorage systems are designed according to the same principle and are composed of the follo-
wing elements:

• A tromplate: a cast iron component, embedded in the concrete, ensuring the transfer of the forces into
the structure and guiding the strands from the sheath towards the anchorage block. It has 1, 2 or 3 levels,
according to the model. All C system tromplates have a rectangular bearing face, in order to fit into thin
webs; those in the K range are square-shaped. In certain units of the K system (A, B or C anchorages), this
component is replaced by a steel or cast iron plate and a trumpet in cast iron, each playing a different
role. The bearing plate may have larger dimensions, depending on the requirements for the structure. The
tromplate has a grouting hole connecting the external bearing face and the inside of the duct. In the case
of the B type anchorage, the grouting hole is located behind the bearing plate, on the cast iron trumpet.
The plate or tromplate is fixed to the formwork by stud bolts, nuts and washers. These same attachments are
also used to fix the temporary cap (cement grout) or permanent cap (casing filled with grease or petroleum
wax). A cardboard leak-proof joint is inserted prior to concreting between the formwork and the tromplate
(or plate). This joint is removed before the installation of the anchorage block. The sheath (or sleeve) pene-
trates the tromplate (or trompet); the watertightness of the connection is achieved using an adhesive tape or
a thermo-retractable sleeve.

In the case of replaceable external prestressing (A’D or AD anchorages), with bare strands, the sheaths
being cement grouted, the tromplate (or trumpet) is fitted with an HDPE trumpet-shaped internal casing, in
order to prevent any bond between the grout and the tromplate (or trumpet) and thus make dismantling of
the anchorage and tendon possible.

• An anchorage block: a cylindrical piece, fitted with conical holes, resting on a tromplate or a bearing
plate. In the case of the C system, the holes are arranged following a parallel grid forming a set of equila-
teral triangles, or following concentric circles, in the case of the K system. The axes of the holes are parallel
to the tendon axis in C system, deviated in K system. These components, made up of carbon steel, are
obtained by machining rolled bars, or forged blocks. The C system blocks are made up of steel with a
nominal ultimate strength of 650 MPa. They can also be fabricated, on special request, from steel with a
nominal ultimate strength from 500 to 800 MPa.

• The jaws (wedges) : conical elements, made up of case-hardened steel, encased in the block holes; they
allow the strands to be secured, by wedging them during the transfer of the prestressing force. They are
identical whatever the nominal diameter of the strand (Ø 12.5 mm – 13 mm or Ø 15.2 mm – 16 mm). The
three components constituting each jaw remain united, from their manufacture until their installation on site,
thanks to a process patented by Freyssinet: this is the “UNIGRIP” jaw.

• The anchorage is a live anchorage (A’ or A anchorages) when all the necessary arrangements are made
to allow the tensioning of the reinforcement : sufficient overlength of strands and an access allowing the ins-
tallation and removal of the jack after elongation of the tendon.

• It is a dead-end anchorage when the tensioning is carried out from the opposite extremity and the ancho-
rage jaws, accessible to an operator, are first manually blocked using a hammer and a tube, then self-lock
when the tensioning starts from the other end.

• It is fixed, embedded in the concrete, when the dead-end anchorage is not accessible (B’ or B anchora-
ge); the jaws are then replaced by threaded sleeves shaped at the end of each strand by means of a threa-
ding press. The sleeves bear on the anchorage block which has cylindrical holes. The whole set is fixed by
a plate, permitting the strand extremities to be correctly positioned; the general tightening is ensured by fas-
tening hooks fitted in the tromplate notches. After completion of the waterproofing, the anchorage is instal-
led amidst the reinforcing bars, then embedded in concrete. This type of anchoring can be advantageous,
since the prestressing force is available just behind the anchorage.

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123. FREYSSINET C AND K SYSTEMS ANCHORAGES

• The fixed anchorage without block or tromplate (NE, NE’, G or V anchorages), with bonded strands th
extremity of which are fitted with bulbs or threaded sleeves, is embedded in concrete. In this case, contrary
to the B’ or B anchorages, the full prestressing force is only available outside the bonding zone. This is also
more cumbersome, because of the arrangement of the bulbs or threaded sleeves, in square or rectangular
patterns.
• The coupler is a mechanical device which ensures continuity between an already tensioned segment of
tendon and its prolongation. It consists of the actual anchorage and a notched rim inserted between the
block and the tromplate (or plate) on which rest the threaded sleeves, shaped at the end of the strands of
the second stage tendon.
– The coupler is a C’ type (C and K systems) when used with a tromplate, or a C type (K system) when used
with a cast iron plate and trumpet set. The assembly is covered by a steel or plastic casing, in order to pre-
vent any bond with the concrete and allow for the second stage tendon to be cement grouted, independently
from the first stage tendon. The supple joint which ensures the watertightness of the junction with the trompla-
te or bearing plate, also prevents any transfer of force to the casing, when the tensioning of the second stage
tendon results in the de-tensioning of the first stage tendon. The casing extremity has a trumpet shape, in
order to deflect satisfactorily the strands and to permit the coupling of the sheath.
– The C’I type (tromplate) or C I type (plate and trumpet) couplers permit the coupling of the second stage
tendon to the first stage one using monostrand couplers, machined or cast iron, with automatic hooking pro-
duced by two inverted jaws and a central spring.
In the case of the K system couplings, a toric deflecting ring permits the transfer of the peripheral strands
from a deflected axis to an axis parallel to the tendon, with no kink in their trajectory when exiting the
block. A steel or HDPE casing isolates the whole coupling zone.

• The monostrand extension makes it possible either to couple a tensioned tendon to a non-tensioned one,
or to join two non-tensioned tendons end to end.
– A similar casing, but longer than that used in the case of the C’I or C I couplers, is used for the R type
end to end joining, in order to allow for the displacement of the pieces when tensioning the two coupled
segments of tendon.

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123. FREYSSINET C AND K SYSTEMS ANCHORAGES

C System

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Système C

Précontrainte Intérieure

Câbles noyés dans le béton

Adhérente

Ancrage

Coupleur

Ancrage

Coupleur

Non Adhérente

Actif

Actif

C System

Internal Prestressing

Embedded tendons

Bonded prestressing

Anchorage

Active

Active

Coupler

Anchorage

Coupler

Unbonded prestressing

Active

A’

Passive

B’

Embedded

NE, NE’, G,

V

R

End to end

joining

C’

Coupler

C I’

Extension

Passive

B’

Active

A’

R

End to end

joining

C’

Coupler

C I’

Extension

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123. FREYSSINET C AND K SYSTEMS ANCHORAGES

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K System

Système K

Précontrainte Intérieure

Câbles noyés dans le béton

Adhérente

Ancrage

Actif

Actif

Coupleur

Ancrage

Coupleur

Non Adhérente

K System

Internal Prestressing

Embedded tendons

Bonded prestressing

Anchorage

Active

Active

Coupler

Anchorage

Coupler

Unbonded prestressing

Active

A or A’

Passive

B or B’

Embedded

NE, NE’, G,

V

R

End to end

joining

C or C’

Coupler

C I or C I’

Extension

Passive

B or B’

Active

A or A’

R

End to end

joining

C or C’

Coupler

C I or C I’

Extension