The post-tensioning technique involves installing and tensioning tendons in a concrete element, thereby applying compressive stress to the material. This compensates for the tensile stress that the concrete may undergo as a result of external loads and reduces or eliminates deformation and cracking.

  • Applications
    Bridges
    Buildings
    Water infrastructures
    Energy infrastructures

A revolution in the art of construction

Post-tensioning has revolutionised the design and construction of concrete structures, allowing thinner concrete sections, longer spans and more durable concrete structures. It also paved the way for the development of new construction methods, making bridge construction simpler, faster and more cost-effective.

The technique was patented by Eugène Freyssinet in 1928. It was developed on thousands of structures across the world by the STUP (Société Technique pour l’Utilisation de la Précontrainte), the company created by Eugène Freyssinet in 1943 – that became Freyssinet in 1976. Post-tensioning is now universally known and widely used.

The use of post-tensioning opens up a wide range of geometric and architectural possibilities. In particular, it allows complex curves, variable elevations and long free spans without support.

Post-tensioning significantly reduces the amount of concrete and steel required for the structure and the foundation work. It allows for the rapid assembly of precast elements using industrialized methods, allowing the site to progress quickly and efficiently.

A post-tensioning solution reduces the need for joints, which in turn reduces joint maintenance. For tanks, silos and reservoirs, post-tensioning results in concrete that is virtually free of cracks and therefore less prone to corrosion problems.

Post-tensioned structures require less construction materials – such as steel reinforcement and concrete – and therefore generate fewer greenhouse gas emissions for their production and transportation. The carbon savings are usually between 20 and 30%.

A solution optimised for every application

Bridge deck and piers, silos, tunnels, reservoirs, parking structures, buildings, stadiums, wastewater treatment plants, marine structures, dams, nuclear reactor containment vessels, cryogenic liquefied natural gas tanks, offshore platforms -and any other structure you can think of!
Full service

Design & build packages  

Find out more in our case studies

Build
France

Arsenal sports center connected post-tensioning

A project to install connected post-tensioning in the roof beams of a new sports centre in France was chosen as the test-bed for a system of monitored site operations which established the technology for wide-ranging data collection.
  • Buildings
  • Post-tensioning
  • Strand system
  • Innovation
+2
BUILD
United Kingdom

Library of Birmingham, PT slabs rather than steel frame

Construction of the library of Birmingham was originally conceived as a structural steel frame. During the tender period, and in order to realise the full value engineering benefits, the frame was changed to reinforced concrete with post-tensioned slabs and beams
  • Buildings
  • Post-tensioned slabs
  • Post-tensioned beams
+1
Build
Hong Kong

TMCLK Link in Hong-Kong: balanced cantilever erection

As part of the design-build project for a set of precast segmental bridges, choice of the erection method was key to its achievement. Opting for the balanced cantilever erection with launching gantry made the difference.
  • Bridges
  • Construction methods
  • Launching gantry
  • Precast segmental bridge
  • Post-tensioning bars
+3
Build
France

New coastal highway prestressed road in La Reunion

On the Reunion Island, Freyssinet teams carried out the prestressing of the viaduct of the new coastal highway, the longest viaduct in France at 5,400 metres.
  • Build
  • Bridges
  • Post-tensioning
  • Heavy lifting
  • Corrosion protection
+3
For over 50 years Freyssinet has been involved in the construction of buildings, optimising their structure using the benefits of post-tensioned slab technology. Our expertise and know-how contributes to the realisation of ever more functional and durable structures.

Advantages of post-tensioning floor slabs

  • Larger slab spans requiring fewer columns and providing more freedom in terms of layout
  • Reduced floor thickness which saves overall height and can thus result in an increase in the number of storeys in the structure
  • Better control of shrinkage cracking for improved watertightness and hence greater durability
  • Reduction or elimination of significant deflection in routine service

  • Savings in materials (concrete and steel)
  • Reduced load on foundations
  • Shorter construction programme due to reduced materials to install
  • Elimination of uneven soffits leading to simple installation of electrical, air-conditioning and other services

The use of floors prestressed by post-tensioning results in a significant reduction in greenhouse gas emissions compared with an equivalent traditional reinforced concrete design.  Optimal savings of the order of 20-25% can be realised.

Application fields

Building floors

Freyssinet’s post-tensioning systems can be used in the construction of the floor slabs for a wide range of building types:

  • Residential buildings
  • High-rise office buildings
  • Shopping centres
  • Underground / traditional Multi-Storey Car Parks (MSCP)
  • Public facilities – hospitals / schools / sports halls

Many of the previously described benefits can be achieved for the benefit of architects, owners and contractors alike, particularly for buildings with large plan dimensions or for high rise structures.

Foundation slabs

Foundation slabs are in direct contact with the ground and enable buildings to be erected on soils with poor mechanical properties.
The undulating layout of the prestressing compensates for permanent and variable loads. The permanent compression of the concrete also improves foundation slab sealing against any water ingress.

Transfer slabs

Transfer structures are often very thick slabs, subject to heavy loading, which absorb the loads from columns above that are not aligned with the columns below. They are generally used in high-rise buildings to clear a space without load-bearing elements or to make the transition to the parking levels.

Prestressing allows the height of the transfer slabs to be reduced considerably; in certain cases, C-Range high-strength tendons for civil engineering will be proposed.

Industrial slabs

These slabs bear on the foundation soil. The prestressed tendons are straight, centered and arranged in both directions.
They allow a reduction in the quantity of passive reinforcement, improve the bending strength and ensure control of shrinkage cracking.
Very large areas can be achieved while reducing or eliminating the number of contraction joints. These joints are vulnerable to traffic wear; their elimination is particularly appreciated when surfaces must be flat to accommodate automated conveyor systems.
The permanent compression of the concrete by prestressing improves its watertightness.

Services tailored to your needs

Design & build packages or technical support

technical support

Range of solutions

Multi-strand PT anchorage system – B Range

The anchorage unit consists of a trumplate, a block and wedges. The cast-iron trumplate is embedded in the concrete and distributes the prestressing load into the structure. The anchorage block rests on the trumplate and the wedges grip the strands.
  • Multi-strand compact prestressing:
    3 to 5 T13 or T15 strands
  • Bonded or unbonded prestressing
  • Separated anchorage block
    for easy installation on-site

Single strand flat PT anchorage system – 1F15 or 1F13

The 1F13/15 single strand system is generally used for unbonded post-tensioning cables. It is made up of (1) Sheathed and greased strand, incorporated directly into the slab before concreting (2) A cast-iron anchorage body with steel wedges, embedded in the concrete which grips the strand and distributes the prestressing force into the structure (3) A plastic connecting tube providing protection to the strand where it is locally unsheathed in the anchorage body (4) A protective cap which is filled with grease and provides permanent protection to the anchoring area.
  • Single strand compact prestressing:
    T13 or T15 strands
  • Unbonded prestressing
  • Adapted to thin floor slabs
    requiring flexible tendon geometry
    using single strand units

B-Range and 1F15/13

Main features
Documentation
Prestressing load
1 to 5 strands with ultimate tensile strength up to 279 kN / strand
Slab minimum thickness
17 cm
Minimum concrete compressive strength
  • B Range for T15 strand: 23.5 MPa (on cylinder) at time of stressing
  • B Range for T13 strand: 20 MPa (on cylinder) at time of stressing
  • 1F15/13: 22 MPa (on cylinder) at time of stressing
  • Certification
    CE Marking no 1683-CPR-0048, according to ETA 06/0226
    Documentation

    Find out more in our case studies

    Freyssinet invented the prestressing, which was a revolution in civil engineering. Our C range offers a solution combining performance and durability for all types of structures.

    Post-tensioning kits under European Technical Assessment

    The post-tensioning kits marketed by Freyssinet are CE marked in accordance with the European Technical Assessment, which ensures product performance, quality control, and state-of-the-art installation methods.

    Freyssinet supply the post-tensioning kits components to compose tendons for internal or external prestressing cables with passive and active ends (anchorage blocks, jaws, caps), as well as the parts embedded in concrete such as trumplates, ducts, couplers when needed.

    Others components are sourced according to applicable standards:

    • Metallic or plastic ducts
    • Steel or smooth plastic pipes
    • Prestressing strands
    • Tendon filling material

    Prestressing steel corrosion protection is essential for the durability of the post-tensioning tendons. It is provided:

    • by a high-quality cement grout and a careful injection for bonded prestressing,
    • or by multi-layer protection given by individually sheathed and greased strands combined with cement grout injection after stressing in the case of unbonded prestressing technique,
    • or by filling the duct by wax for external (unbonded) prestressing tendons composed of bright steel strands.

    Tensioning kit

    Choosing expertise and service

    The C-range is the Freyssinet state-of-the-art prestressing solution for civil engineering. Optimized for every application, it complies with the most stringent requirements in terms of performance and durability.

    Post-tensioning teams

    The C range anchorage blocks are the smallest component of all existing prestressing kits, allowing to significantly reduce the size of the embedded trumplate in the concrete. Their surface area is 60% smaller than the traditional PT system using a bearing plate, allowing to:

    • reduce the width of the beams and webs of the concrete box girders
    • increase the distribution of the prestressing tendons
    • reduce the distance from the concrete edge

    Freyssinet C-range system is used to compose prestressing tendons units from 3 strands (GUTS: 837 kN) to 55 strands (GUTS: 15345 kN).

    15 mm (15.3 or 15.7) strands of all steel grades (up to 1860 MPa) in bright steel or individually greased and sheathed strands.

    The C-range was developed by Freyssinet 30 years ago. It has been continuously improved and adapted since then to suit the projects’ needs worldwide.

    Expected lifetime of 100 years.

    Thousands of applications worldwide.

    The prestressing system allows to provide PL1/PL2/PL3 protection levels as defined in fib bulletin 33.

    Certificate of Constancy of Performances No 1683–CPR–0048 described in ETA No 06/0226

    By choosing Freyssinet, you will collaborate with a PT specialist, that can provide design services, in-house manufacturing, testing and site installation, or only expertise and knowledge where you need it.

    Technical configurations

    / Bonded internal prestressing

    This is the most common application. It is based on the use of an uncoated strand (bare steel) in a corrugated metal sheath and injected by cement grout.

    Depending on project requirements, different configurations can be chosen, such as:

    • the use of a corrugated plastic sheath for aggressive environments,
    • Liaseal® duct coupler for precast concrete structures,
    • full encapsulation systems for electrical isolation.

    / Unbonded internal prestressing

    Unbonded prestressing tendons offer multi-layer protection against corrosion. They allow the prestressing force to be measured, adjusted if necessary and the tendons to be de-tensioned or replaced if required.

    When using bare strands, the injection material is usually wax.

    The use of individually greased and sheathed strands contained in HDPE pipes, which are injected with a cement grout before tensioning, increases the durability of the prestressing tendons.

    / Unbonded external prestressing

    External prestressing is well suited to thin concrete structures; it also allows easy inspection of tendons.

    The most common application is based on the use of strands placed inside thick sections of HDPE pipes, mirror-welded and injected with cement grout.

    To allow tendon removal, the ducts pass through a recess or a double casing at the anchor diaphragms and deviators.

    Two solutions are commonly used to increase durability:

    • Use of individually greased and sheathed strands placed in a plastic pipe injected with cement grout before tensioning.
    • Use of bare strands placed in a plastic pipe injected with wax after tensioning.

    Products supplied by Freyssinet

    Compact anchorages

    Active or passive anchorages consist of cast iron trumplates, anchorage blocks, wedges and plastic or cast-iron injection caps.

    They are used to compose external or internal tendons, with bare or greased strands and HDPE sheathed strands, from 3 to 55 strand units (from 837 to 15 345 kN GUTS). They are implemented with an additional length of strands at the tensioning end.

    Different functionalities are possible: encapsulated, electrically insulated, replaceable, retensionable.
    • Wide range of civil engineering applications,
      including cryogenic use
    • Expected lifetime of 100 years
    • Any protection level
      as required by the project specifications

    Dead end anchorages

    They are installed at the end of a tendon in areas that are not accessible after concreting. This implies that they must be carefully installed before concreting, in order to minimise the risk of strand slippage during tensioning.

    Three types of dead-end anchorages are possible, depending on the number of tendons, units, construction sequences and local standards (1) Anchorage block with cylindrical holes and swages at strand ends, held in position by a retaining plate (2) Steel plate with cylindrical hole(s) and swage(s) at strand end(s) (3) Dead-end anchorage obtained by deforming the 7-wire strand into an “onion” shape.
    • For areas not accessible
      during stressing phase
    • Specific provisions to be taken
      when installing the system

    Couplers

    The couplers connect two tendons which are tensioned one after the other after two separate concreting phases.

    For multistrand coupling, they are made of machined steel with two sets of opposing conical holes.

    A cast-iron model is available for the individual coupling of each strand.
    • Allows a PT tendon to be lengthened,
      depending on the construction phases
    • Single-strand couplers (with anchorage blocks)
      or multi-strand coupler can be used as fixed couplers
    • Single-strand mobile couplers are used for
      the strands that make up the tendon extension

    LIASEAL -Seal system for match-cast segments

    The construction of a segmental bridge involves assembling the post-tensioning duct segment by segment.

    The Liaseal system is a duct coupler that ensures the continuity of the duct between the match-cast segments.
    • Coupler for corrugated plastic duct
    • Full encapsulation of
      the prestressing steel (with plastic duct)
    • Can be used for electrically-insulated tendons

    1F15 anchorage for single strand prestressing needs

    It allows the anchoring of a single-strand cable in thin civil engineering elements, such as bridge decks for transverse post-tensioning.

    The cast-in anchor unit combines the function of an anchor block and a prestressing force diffusion plate.

    It is particularly suitable for unbonded internal prestressing configurations.

    1F15 anchorage for single strand prestressing
    1R15 anchorage for single strand additional prestressing

    1R15 anchorage for single strand additional prestressing

    See the repair section of the website for detailed information.

    1X and 2X anchorages for additional prestressing of circular structures

    See the repair section of the website for more detailed information.

    These are specific anchorages for the active strengthening of circular structures such as silos, tanks, chimneys, cooling towers and pipes. These anchorages consist of post-tensioning cable hoops that apply pressure to the structure to be reinforced.

    The hoop anchor consists of a cast iron element resting on the circular structure and serving as an anchorage at both ends of one or two hoops:

    • The 1X anchorage is used to make a prestressing hoop on a structure with a radius up to 27,5m.
    • The 2X anchorage is used to anchor 2 hoops, each wrapped once or twice around the structure with a radius of up to 5.5m.

    The system is suitable for unbonded external prestressing configurations (strand greased and sheathed in HDPE duct, grouted with cement before tensioning)

    1X15 anchorage for additional prestressing of circular structures

    Our references

    Download our brochures

    Documentation

    Freyssibar® prestressing systems

    Prestressing bars are a simple and efficient solution for securing and tying down structural elements together or transferring compressive forces to generate the necessary friction between the surfaces in contact.

    Freyssinet has been implementing Freyssibar® systems since 2005. The range is engineered to meet all the needs and challenges facing the construction industry, from the most standard cases through to the most demanding applications.

    We provide end-to-end services, including design studies, in-house manufacturing, installation, inspection and maintenance, or sale only depending on your needs.

    • Permanent or temporary prestressing
    • Internal (bonded or unbonded) or external prestressing
    • Replacement, retensioning, monitoring, encapsulation, etc

    • Bridges and viaducts
    • Marine works
    • Nuclear plants
    • Wind turbines
    • Oil and gas infrastructure
    • Temporary construction systems
    • Heavy lifting and handling
    • Geotechnical applications

    • Concrete
    • Steel
    • Masonry
    • Timber

    • Passive or active anchors
    • Restressable
    • Removable
    • Replaceable

    • Wide range of bar diameters
    • Different grades of steel including high strength capacity
    • Customized options such as prefabricated solutions or simple anchorages for temporary structures

    • European Technical Assessment: ETA 09/0169
    • CE Marking: 1683-CPR-0052

    System components

    Freyssibar®

    The bars are hot-rolled from high-strength alloy steel. They are subsequently cold worked by stretching, then threaded over their full length by cold rolling to ensure high fatigue resistance and low susceptibility to corrosion. Every bar is stress-tested to 85% of its guaranteed ultimate tensile strength.

    The bars are available in maximum lengths of 11.8 m, in diameters 26.5 to 50mm. For longer lengths, bars can be connected together using extension sleeves.
    • Guaranteed strength thanks to the
      stretching operation during production
    • Control of losses during stressing
    • Product available on stock
      Accurate and easy assembly on site
    • Jacking
    • Moving heavy loads

    Freyssibar®+

    The bars are produced using a heat treatment process that delivers enhanced mechanical performance. They offer a superior combination of mechanical strength and ductility as compared with conventional prestressing bars.

    The bars are available in maximum lengths of 11.8 m, in standard diameters 55 to 97mm (other diameters on request). They are supplied with threaded ends; the thread length can be adjusted on request.
    • Very high capacity bars available
      (diameters > 100mm on request)
    • High ductility - elongation at break of 10%
    • Tensioning with light equipment
      Resistant to very low temperatures
    • Strapping and lifting operations
    • Seismic protection

    Freyssibar characteristics

    Freyssibar configuration

    The Freyssibar and Freyssibar+ systems include a wide range of threaded bars and associated anchoring, coupling and extension devices.

    Couplers

    Mobile couplers are used to connect two bars together on their main run. The duct is adapted by the coupler to provide unhindered movement during tensioning.
    A fixed coupler is used to extend a prestressing unit already under tension by screwing a coupler to the end of the bar protruding from the anchor. In this case, the coupler barely moves during tensioning. A special cap is used to ensure a continuous duct.

    Freyssibar - Couplers
    Freyssibar - Anchors

    Anchors

    The anchors are designed to anchor the force in the bar and transfer it to the structure.
    The flat anchors, used in most cases, consist of a straight nut, a washer and an anchor plate. A groove in the anchor plate allows the injection product to circulate between the duct and the cap.
    Spherical anchors compensate for perpendicular alignment issues between the bar axis and the bearing surface when used on existing structures: up to 3° for type 1, other cases for type 2.

    Protection against corrosion

    The alkaline nature of the grout renders the steels into a passive state. It produces bonded prestressing.

    It is used for unbonded prestressing, so that the residual prestressing force can be checked over time. The bar can be re-tensioned or replaced if necessary.

    Freyssibar - Corrosion protection - Wax injection

    It can be used for external prestressing. Thanks to the compact design, the bars can be introduced in small holes.

    The protected bar is positioned directly in the rebar arrangement and equipped with its embedded anchor. It is often used to anchor a metal structure to a solid concrete foundation. The compact design allows for easier fitting into a dense reinforcement.

    Freyssibar - Corrosion protection - By wax tape during prefabrication

    Services tailored to your needs

    Full service or ... supply only

    supply only

    Download Freyssibar+ Technical Datasheet

    Documentation

    Main use cases

    Prestressed structures

    Freyssinet bar systems are widely used to create prestressed structures, especially for repair and strengthening.
    • Bridges, dams
    • Buildings
    • Civil engineering structures

    Blisters

    When fitting additional prestressing tendons to existing structures, sheaves and deviation points need to be created. The anchoring system for the ends of the tendons is fitted to the sheaves, while the main runs are guided through the deviation points. In this case, Freyssinet prestressing bars are used to fix the sheaves to the existing structure that needs strengthening by generating a transverse nailing force that creates the necessary friction between each sheaf and the structure.
    • Bridges decks
    • Beams
    • Slabs

    Anchoring structural elements

    To create a stable and long-lasting joint between structural elements, such as securing steel and concrete components, they can simply be tightened together with prestressing. The Freyssinet system ensures a long-term compression joint.
    • Wind turbines
    • Towers
    • Antennas

    Assembling precast elements

    Whether for temporary or permanent applications, Freyssinet bar system offers a simple and effective solution for assembling concrete elements with prestressing bars.
    • Viaducts built with launching gantries
    • Floating caissons, bridge piers, silos
    • 3D-Printed buildings

    Moving heavy loads

    The Freyssinet system and its accessories are easy to use and deliver superior strength and reliability for moving heavy loads. The system transfers the force that is required to move the structure using extremely light equipment.
    • Sliding, pushing
    • Hoisting
    • Driving

    Connection with a foundation

    Micropiles and post-tensioning bars can be combined to create a simple and effective foundation for an existing or precast structure. The prestressing bars create a friction joint between the structure and the sole plate, which is built on micropiles, without the need for a complex and dense arrangement of reinforcement.
    • Bridge piers
    • Columns

    Fixing launching noses

    Fixing a launching nose to a deck requires the use of high prestressing forces in a confined space. Designers are often faced with the problem of how to arrange the bars in the available space. The wide range of possibilities offered by Freyssinet bar systems makes this process much easier, since they improve the forces applied to each assembly while reducing the number of bars.
    • Incrementally launched bridges
    • De-launching

    Carriage form travelers and launching gantries

    When it comes to temporarily fixing a carriage form traveler or launching gantry, a quick, easy and reliable solution is needed that can be used over and over again. The Freyssinet system ticks all the boxes, which explains why its use has become widespread.
    • Construction of bridge decks
    • Decks

    Fixing brackets

    The principle of transferring the load from a bracket to a structure by friction can be achieved using prestressing bars. Controlling the force applied during the process is essential for the performance of the joint and the safety of the structure.
    • Jacking structures
    • Widening pier caps and decks
    • Balconies

    Find out more in our case studies

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