Invention of future VSL systems, products and services to serve our clients

  • Lisboa Palace
    Construction of a large diaphragm wall for a new hotel and casino complex.
    Hong Kong - 2014 read more

    Lisboa Palace

  • Shatin to Central Link contract 1106
    Diaphragm wall and barrette construction for the extension of Diamond Hill Station.
    Hong Kong - 2014 read more

    Shatin to Central Link contract 1106

  • Wai Yip Street
    Construction of a diaphragm wall and associated works for a commercial building development.
    Hong Kong - 2014 read more

    Wai Yip Street

  • Tseung Kwan O to Lam Tin Tunnel
    Site investigation using horizontal directional coring (HDC) techniques and in-situ testing.
    Hong Kong - 2015 read more

    Tseung Kwan O to Lam Tin Tunnel


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Creating solutions together

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A dedicated VSL R&D team works on the research and development of systems, equipment and methods that are considered strategic for the group as a whole.

Individual regional, profit centre or project-specific R&D activities are also carried out, often with the support of staff from the VSL Technical centres and coordinated by the VSL R&D manager. In parallel with these R&D activities, there is innovation every day as part of work carried out at all levels throughout the VSL Group, encompassing all types and aspects of its activities.

Ideas for R&D topics or needs and their basic requirements are generated within the VSL global network and by listening to clients’ needs. Sustainability, environment, safety and reliability are key aspects considered in any R&D activity.

Innovations in post-tensioning

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VSL’s GC anchorage

A recent example of R&D in post-tensioning systems has been the development of the GC-type anchorage system. The system’s cast iron bearing plate is an evolution of earlier types of VSL bearing plates. It has been optimised to meet the latest requirements for PT systems, such as those specified in the European Guidelines for Technical Approval of PT kits (ETAG013). The GC anchorage system was designed by VSL’s R&D team and initially tested in-house. Once the design was confirmed, its performance was verified by tests in accordance with ETAG013 carried out at external accredited laboratories.

Developments in stay cables

A long-standing and key strategic topic for R&D is the VSL SSI 2000 Stay Cable System. Development of the SSI 2000 anchorage system and the single strand installation method took place in the late 1990s and a recent focus has been on the development of a saddle system that complies with the most stringent system requirements, as for anchorages. The result of this development is the SSI 2000 saddle, which guides each strand individually through the saddle in an individual void created inside Ductal® ultra-high performance mortar. The V-shaped form of the void significantly improves the friction between it and the strand and therefore ensures transfer of unbalanced loads in strands from both sides of a pylon. A full-scale saddle system for a 55-strand cable has been successfully tested in accordance with International Federation for Structural Concrete (fib) recommendations. The tests took place in summer 2009 at the laboratory of the Technical University of Berlin.

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VSL Saddle testing
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VSL’s Friction Damper

Another focus of VSL R&D has been on the control of vibrations of stay cables. Today the VSL Group can offer several different solutions to its clients. The VSL Friction Damper was developed in cooperation with a consultant who proposed the concept for the damper and the design procedures. This damper system provides very high damping ratios through friction between parts of the cable and the supporting structure, which move relative to each other.

More recently, VSL entered a partnership with a Japanese company and now offers VSL R-dampers, a damper system that uses special pads made of high-damping rubber to dissipate energy through shear deformation of the pad. The VSL R&D team verified the performance of these systems in full-scale tests and has produced the relevant design tools.

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VSL’s R-damper

VSL has carried out further development of the installation methods used for stay cables. The VSL SSI 2000 compact system uses special tools and installation methods to permit installation of stay cables in compact stay pipes, which significantly reduce wind loads on the cables. The VSL SSI 2000 stay cable system protected with dry air provides the lowest wind-drag forces of any system presently on the market – another jewel in the history of VSL R&D.

Taking the lead in durability

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Electrically isolated tendons on Roeti Bridge in Solothurn, Switzerland

VSL R&D has long since focused on improving the durability of VSL systems. It was VSL R&D that introduced robust plastic ducts (PT-PLUS®) for full encapsulation of post-tensioning cables towards the end of the 1980s – long before the durability of tendons attracted the attention it now has. This was followed by the development of the CS2000 anchorage system, which extends complete encapsulation to include the anchorage zone and includes connections that are compatible with PT-PLUS®. VSL R&D then introduced Electrically Isolated

Tendon (EIT) technology to multistrand tendon systems in general and the CS2000 system in particular. EIT technology allows the quality of the encapsulation to be monitored and thus helps ensure the protection and durability of the tendon. Fully encapsulated tendons and EIT have since become the industry’s recommended protection measures for post-tensioning tendons, incorporated in fib recommendations. VSL has invested significant R&D efforts in grout materials and grouting procedures to ensure complete filling of tendons. A special sensor has now been developed to check for complete filling of the tendons at specific locations in real-time during grout injection. The same sensors can later be used to confirm whether or not corrosion is occurring inside the tendon duct near the sensors. This sensor system offers a new level of tendon monitoring to ensure durability.

New technology for nuclear requirements

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Full-scale mock-up for nuclear applications in Gien

VSL has recently completed a major R&D project for the use of post-tensioning systems in the latest generation of containments for EPR nuclear plants. The project included development and testing of specialised anchorage systems for 55-strand tendons as well as development of installation and stressing equipment. This ensures that all strands have the same forces after stressing, even where there are significant tendon deviations to form a complete circle.

Special monitoring features were also developed to allow real-time recording of stressing and grouting data. VSL built a 46m-diameter mock-up in the town of Gien in France. The full-scale mock-up was used to test the installation, stressing and grouting procedures as well as compliance with specifications. After successful completion of the test programme, the mock-up was handed over to the town of Gien which will now use it as a stormwater reservoir – a truly sustainable R&D project by VSL.

Wind turbine tower construction
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VSL is playing a key role in the construction of wind turbines, from tower foundations to the installation of nacelles and blades. Its extensive experience in the design and engineering of concrete structures has proved directly applicable to wind energy projects and has led to the development of two innovative heavy lifting techniques for the turbines.

Lifting the nacelle and blades

The alternative installation methods are based on a custom-designed self-climbing frame that brings many advantages. The frame is secured at the top of the tower, from where it lifts the nacelle and blades. The technique avoids the need to set up heavy cranes, replacing them with lightweight equipment that is custom-made for each application and can be easily transported and assembled.

The VSL Telescopic method®

VSL has developed an original construction method that telescopes tower tubes one inside the other and uses heavy lifting solutions with strand jacks to raise them into position. The solution takes advantage of the permanent structure and keeps the use of temporary works and cranes to a minimum. The benefits of the telescopic method can be summarised in three words: safety, optimisation and capacity.


Ground investigation

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Swivel arrangement so that drill rod can turn while the-core catcher and outer casing remain stationary

VSL’s steerable core barrel enables continuous coring that follows a predetermined alignment (such as the one for a proposed tunnel) to ensure accurate assessment of the ground conditions. The aim is to provide a system for more accurate detection of faults, large seepage zones or other features so that risks and project costs could be better evaluated. In particular, VSL wanted to enable continuous rock coring along a sub-horizontal curved alignment for ground investigations on projects such as tunnels and mines.

VStrip, the VSL polymeric strip: connection to concrete facings

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To ensure full load transfer between facing and fill reinforcement in the VSoL® Polymeric wall system, VSL developed an innovative solution to connect VStrip reinforcement to concrete facings. The VStrip connection is simply a U-shaped internal slot at the rear of the concrete facing, formed by reusable void formers during concreting which the VStrip is inserted through during installation The VStrip connection has been tested extensively by VSL to prove its efficiency and to optimize the associated panel reinforcement details.

The VStrip connection does not require any additional cast-in items and rebar requirements for the connection are part of the overall reinforcement requirement for the facing. By adopting this approach, the VStrip connection provides the most economical and practical connection solution which is fully proven by testing and trials. The innovative VStrip connection concept has been patented by VSL.

Monitoring FT Laboratories’ total solution for structural health monitoring

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FT Laboratories’ Structural Health Monitoring System (SHMS) Total Solution provides a comprehensive approach for data collection, presentation, processing, evaluation, rating and reporting. It starts by monitoring the loading and structural parameters using real-time data sensors. The information can be used to evaluate the bridge’s structural performance and to plan a comprehensive structural inspection programme. It can also be used to determine the cause of any damage, as well as the extent of any remedial work required.

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Schematic Diagram of FT Structural Health Monitoring System Total Solution

The Total Solution extends data interpretation through integration with the latest information and structural analysis technologies. It overcomes the limitations of a file-based system by introducing an additional module - Structural Health Data Management System. This module enables better control and eliminates redundancy by integrating data and information files for efficient retrieval and easy maintenance. There is automatic input of measured and processed data such as the wind spectrum, accelerations, GPS displacements and dynamic strain data. Automated plotting of 3D time-series data is used to determine the deformation pattern of the structure under loadings. Automatic synchronised processing can be carried out for different types of correlation analysis and pattern recognition.


Bringing knowledge together

The collection of best practices and their documentation in VSL Field Manuals is another important activity of the VSL R&D team. The VSL Field Manual for post-tensioning systems forms the basis for the training and certification of VSL site supervisors at the VSL Academy. For issues not covered by the Field Manuals, the R&D team acts as the knowledge centre for all VSL entities and staff. The team answers any questions related to VSL systems, equipment and methods as well as helping with troubleshooting.

Many of the results of VSL’s R&D work are protected by patents. The VSL Group has more than 30 families of patents that are granted or pending.

The VSL Group regularly invests about 1% of its turnover in R&D at group level.

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