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FORMWORK

VSL has experience in a wide variety of specialised formwork systems, including climbforms for pylons or building cores, forms for tanks (water and LNG/LPG), and precast units, especially for bridges.

  • Tuas West Extension project
    VSL’s involvement in a technically challenging project, consisting of 7.5km of twin viaduct, four above-ground stations and a depot.
    Singapore - 2013 read more

    Tuas West Extension project

                     DOWNLOAD PROJECT REFERENCE(S)
  • HK-Zhuhai-Macao Link's tunnel section - Focus: Immersed tunnel segments
    VSL's technical centre in Asia develops a sliding system for immersed tunnel segments.
    China PRC - 2008 read more

    HK-Zhuhai-Macao Link's tunnel section - Focus: Immersed tunnel segments

                     DOWNLOAD PROJECT REFERENCE(S)
  • Lower Shing Mun Reservoir
    Draw-off tower construction with VSL design, supply and operation of the climbform system.
    Hong Kong - 2009 read more

    Lower Shing Mun Reservoir

                     DOWNLOAD PROJECT REFERENCE(S)
  • Veronne Apartments
    Post-tensioning and Climbform design and construct.
    Australia - 2002 read more

    Veronne Apartments

                     DOWNLOAD PROJECT REFERENCE(S)

Concrete construction makes extensive use of formwork and there are many suppliers and systems that are available on the market.

However, complex or major structures often require specialised formwork that addresses specific needs or requirements such as:

  • complexity and shape, as for example in the case of bridge segments, where conventional forms cannot be used efficiently
  • size or volume, which is the case when buildings or bridges need heavy beams that require the design of special forms
  • work of a repetitive nature, such as the central core of a high-rise building, which often requires a short cycle time to reduce the construction schedule by using self-climbing formwork to minimise the use of cranes

VSL has considerable experience in the design, supply and commissioning as well as the operation of a wide variety of specialised form systems that provide the answers to these specific needs.

Services VSL offers

VSL provides specialist formwork systems for use in a variety of applications including:

    • Building

Specialised formwork may be required for different areas of a building’s construction:

      • VSL self-climbing form systems can be used to build the central structural core of high-rise buildings, where short cycle times are required to reduce the construction period. Use of cranes to move the formwork has to be reduced as much as possible, leaving the cranes for other construction tasks. Typical cycles of three to four days per floor can be achieved consistently using self-climbing formwork, which provides a safe and efficient environment.
      • VSL provides specific formwork systems to precast heavy structural elements such as beams and columns.
    • Tanks

VSL has developed jump-form systems that provide benefits to the contractor when casting circular tanks such as those for liquefied natural gas (LNG).

    • Bridge construction

Precasting is widely used in bridge construction as the work is often repetitive and involves installation of many heavy elements. Specialised formwork is generally custom-built for casting or precasting different structural members, such as:

    • Precast beams, precast piers and precast crossheads
    • Precast segments, which can be prefabricated in short or long lines - VSL has extensive experience in both. They are match-cast and post-tensioned.
    • Precasting of full spans is generally used for very repetitive, long and straight structures. Examples include projects such as Taiwan’s high-speed railway.
    • Prefabrication of bridge piers ready for assembly in the field can make sense where access is difficult or where labour rates are high. Such precasting requires the elements to be match-cast and post-tensioned together.
    • Bridge pylons, especially for cable-stayed structures, require special formwork which may be either self-climbing or use jump forms. VSL has extensive experience in self-climbing formwork that provides a safe working area at all times, including during the climbing operation. It allows fast erection cycles as low as three to four days.
    • Segments may be cast in situ, using form-travellers. VSL has developed its own modular form-traveller system that allows reuse of the supporting frame. The form skin and support are generally custom-made to accommodate each project’s geometry and sizing.
    • Full spans may be cast in situ using movable scaffold support systems (MSS). This technique is less developed but can prove to be efficient for some projects. It generally requires complex and heavy self-launching forms, for which VSL also has considerable experience.

For all these specialised formwork systems, VSL provides a full turnkey service to clients including:

  • Defining the formwork requirements
  • Developing the precast yard layout
  • Integrating the formwork into the casting yard
  • Definition and design of the rest of the temporary works, including - but not limited to – the rebar jigs, spreader beams and storage areas
  • Formwork design and shop drawings
  • Fabrication
  • Assembly and commissioning
  • Operation

Associated services

In addition to the formwork, VSL provides turnkey services in construction including:

  • Design of permanent structures
  • Construction engineering, stage-by-stage analysis and geometry control
  • A range of construction services right through to the management of the full project

Advantages of VSL’s solutions

Efficiency based on a large experience

VSL has experience spanning across the whole construction process, from initial design to final delivery of the completed structure. As such, VSL integrates details into its formwork systems that make the equipment safe to use, user friendly and highly efficient.

A complete and integrated service offering

VSL not only provides the equipment but also all the associated services, including operation of the system. This brings efficiency to project interfaces that would otherwise have to be managed.

Contributing to sustainable solutions

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Although VSL formwork is generally designed for special custom-made applications, VSL is always aware of the need to reduce the use of raw materials. It strives to standardise the main frames and hydraulic and mechanical components that are used to operate the equipment.

For the self-climbing formwork used for high-rise building cores or bridge pylons, standard equipment is reused from one project to the next. This includes hydraulic equipment such jacks, pumps and control boards as well as the mechanical elements such as rollers, main brackets and frames. Only the formwork skin and some custom-designed members need to be scrapped at the end of a project.

VSL has also developed modular form-traveller equipment. Although these are generally heavier than is strictly necessary for a project, they allow the entire supporting frame to be reused from one project to the next.

Finally, safety is always a major concern for specialised custom-made equipment. VSL is well aware of this and such concerns are taken into account from the very early stages of equipment choice, allowing for safe working areas at all stages of the construction process.

Self-climbing formwork system (for pylons and central building cores)

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One Island East project, Hong Kong

VSL self-climbing formwork systems are designed to be modular and lightweight and to provide clear, unobstructed access to all working areas. Their mechanised, self-climbing design facilitates the casting of highly complex structures with variable geometry while producing the high-quality finishes required by clients. The VSL Climbform System achieves optimal cycles of three to four days per lift, with one lift generally equalling one floor. The modular arrangement of the system means that variable lift heights can be accommodated with relative ease up to a maximum height of about 6m.

The basic system

The VSL hydraulically self-climbing system consists of standard modular components. They are designed to lift the complete enclosed platform areas in a quick and safe operation.

The components can be preassembled in large pieces on the ground for the initial set-up, but can be dismantled into smaller pieces after the final operation to minimise the required crane capacity. A simple level-control system ensures a safe lifting process.

Trailing platforms are added one level below to allow finishing of the concrete surface and closure of openings underneath the form level. This allows the structure to be completed and finished as the climbform rises, avoiding the need to return later to finish the work using working platforms or other access methods.

The main components are standardised for pour heights of up to 4m but can also accommodate higher lifting steps if required.

A standard feature is the provision of safe access from the main platform to the top working and trailing platforms. The platforms may also be used for storage of materials such as reinforcement.

Main components

The main components of self-climbing formwork are :

  • An upper main steel frame to support the forms and working platforms that closely following the geometry of the structure to be built
  • Hydraulic jacks and pumps to move the system. The jacks have a long stroke of 4m or more and act on the previously poured concrete walls, lifting the entire system from one level to the next.
  • The main frames encasing the hydraulic jacks support the main steel frame at the top, and include the self-securing system that supports the entire form system between the lifts throughout the rebar, formwork and concrete operations.
  • The form itself, which is on rails and provides space for rebar installation and any recesses in the forms
  • Trailing platforms below the formwork so that work can take place to finish the concrete operations below.

How it works

All elements of the climbform are connected to a top frame that is pushed up by hydraulic jacks bearing on walls that have already been completed.

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Reinforcement fixing takes place on a safe working platform.
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The working platform is raised for the concrete works.

Safety

The system is inherently safe as it rests on the parts of the structure that have already been completed and bears on this structure as it climbs to the next level.

All working areas are provided with generous access and with working platforms that are enclosed, providing a very safe working environment.

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Safe working areas are provided
around the walls being built.

Optimised working cycle

To optimise the working cycle for each project, the system has the flexibility for the outside formwork of the building’s walls to be climbed together with the inner formwork or to be lifted separately.

Other considerations that are taken into account include scope for different pouring heights as well as steps in wall thickness and the preassembled reinforcement cages. In coordination with the client, VSL can cater for options such as introducing a concrete placing boom into the climbform and adding openings for prefabricated stairs and stair towers.

Precast Segment and Beam Formwork

For the precasting of structures such as buildings or bridges, VSL provides the design, fabrication and operation of casting cells, which can be operated individually or as part of a short or long match-casting line.

Individual formwork is generally used for precast beams or elements that are to be joined with cast-in situ stitches.

Short or long match-casting lines allow precast elements to be cast one against the other, so that they match exactly when reassembled in the field. The joints in between are generally glued during erection with an epoxy-based material, which acts as a lubricant during the assembly and eventually seals the joint for better durability of the structure. These elements are finally secured together with the use of post-tensioning.

Short-line casting

Short-line casting is used where there are changes in the curvature in plan and/or in elevation of the structure to be built.

Long-line casting

Long lines are used mainly when the structure has fixed curvatures in plan and in elevation.

The casting yard can be used to create segments for either span-by-span or balanced cantilever construction ready for reassembly in the field.

Form-travellers for cast-in-situ balanced cantilever bridge structures

Form-travellers allow segments to be cast in position by moving the formwork from one segment to the next. The system is supported by a frame that rests on the previously erected segment.

Climbform

Modular climbforms are used for

  • bridge pylon or pier construction, and
  • the central cores of buildings

The pier heights, available crane capacity and demands of the site schedule determine whether jumpforms or automatic climbing systems are chosen for a bridge’s piers and pylons.

VSL provides modular components to cater for different types of lifting operations and pier and pylon shapes. Top working platforms can reach more than two levels above the current work to allow safe assembly of the overlapping reinforcement. Trailing platforms can be used for finishing the concrete surface and closing any openings.

Preassembled reinforcement cages can be adopted and cross beams or solid pier heads can also be catered for. Pouring heights of up to 6m can be accommodated: Cycle times of 3-4 days per section can be achieved on a regular basis.

Use of a ‘smart’ formwork solution minimises the time spent on adjustments between sections.

Safe access is ensured from the main platform to both the top and trailing working platforms. The platform can also be used for materials storage if appropriate.

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Climbform was used for the back-span piers of Stonecutters Bridge, Hong Kong.
The central building core of the AIG Tower in Hong Kong was built using VSL Climbform.
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Slip-forming for pylon and cores

The slip-form system can be used to build bridge pylons or building cores.

Pouring rates are approximately 0.3m/h

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Construction of the approach span piers at Tsing Ma Bridge, Hong Kong
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Jump-form

For short piers, a crane-lifted jump-form is a very fast and flexible solution. The inside and outside forms are lifted separately and are optimised for assembly of the reinforcement. The components are easy to assemble and simple in operation. Even shapes that are inclined forwards or backwards can be constructed using a jump-form. The inside platform of hollow piers and pylons can be climbed by single climbing platforms or using a complete inner platform.

Precasting cells for bridge segments

Casting cells for bridge segments

Casting cells are used when concrete segments or beams are not cast in situ on site. Casting cells are used for segment lengths from approximately 2m to 5m. The cells are robust and they can be relied upon to keep their geometry. Components can be adjusted to cast variable shapes in the casting cell. VSL casting cells are designed for multiple and fast assembly and stripping operations. Inserts for post-tensioning and segment handling can be included, as well as shear keys in the bulkheads.

Short-line casting
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Hodariyat Bridge in Abu Dhabi was built using short-line casting for the main span segments, which are 36m wide. The segments were each set in position to allow match-casting of the next one.
Long-line casting
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The long-line casting method has been used on the Metro de Santiago in Chile.
Pakse in Laos adopted the long-line casting method.
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Bridge pier precasting – casting cells in long lines

Access can often be difficult in congested areas such as cities. This may lead to the piers being precast before assembly and post-tensioning on site.

Long-line precasting can be set up for this, with the segment length depending upon the transportation and lifting capacity of the equipment available.

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Precasting formwork was set up for the Hodariyat Bridge in the UAE to allow use of the long-line method for segments of the approach piers.
Segments were precast for the approach piers of the Hodariyat Bridge, UAE.
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Precasting of pier segments for the Hodariyat Bridge in the UAE simplified erection.
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Moulds for precast beams

The moulds used for precast beams can reach in excess of 30m in length. VSL provides moulds for straight, curved and spiral beams that feature fine adjustments and are ideal for monorail beams. Superelevation is taken into account and the moulds are also provided with adjustable soffit forms to cater for convex and concave beams. Inserts such as voids, PT ducts and finger plates can be easily fixed. The design takes into account the requirements for curing and post-tensioning of the beams in the moulds. Adjustable bulkheads complete the efficient and accurate solution.

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Precasting of the main beams for a cruise terminal in Hong Kong required the use of special formwork shaped like a water drop to achieve the design created by world-renowned architect Norman Forster.
Precasting of the special main beams at a cruise terminal in Hong Kong required the external form to be fitted with vibrators.

For the Venetian Macao Sands casino project, VSL made extensive use of precasting for the beams and planks. More than 9,000 units were erected in a record time of 13 months.

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Extensive use was made of precasting for beams at the Venetian Macao Sands project.
Erection of precast elements at Venetian Macao Sands
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Cast-in-situ sections were used in conjunction with precast beams.
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Full-span precast

It can make economic sense to precast full spans in some cases, particularly for industrialised production of very long bridges with relatively straight alignments. An ideal application is building the long structures needed for elevated high-speed rail lines. Casting cells for full spans tend to be complex, with little room for access for operations such as installing the rebar cage.

VSL has built up extensive experience in this type of equipment, and has successfully built and operated such formwork.

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Full-span precasting was used for the C215 contract in Taiwan.
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Form-travellers for cast-in-situ structures

Cast-in-situ cantilever structures built with form-travellers are very popular worldwide, as this method is very flexible, and allows the economical construction of long structures over congested sites or in areas with difficult access.

As the formwork can be adjusted at each segment, the alignment closely matches the theoretical casting geometry.

The method is highly reliable and does not require specialist skills to define and monitor the bridge geometry.

VSL has developed its own modular form-travellers that enable casting of most structures of this type. The specific needs of a project can be met with only a few changes to the bracings and inner and outer formwork from one project to the next.

VSL owns many of these travellers worldwide and provides a turnkey service to its clients, covering the supply and operation of this equipment together with supply and fabrication of the formwork.

These structures are generally post-tensioned during construction.

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A modular form-traveller system was chosen for the C215 contract in Taiwan.

The Gateway project in Australia has a 250m-long central span and the segment depth at the pier is 16m.

VSL designed a new traveller to achieve the short cycle time required by the construction programme. The patented innovation allows the rebar cage to be prefabricated and dropped into the webs.

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A new modular form-traveller system was developed to cater for the 16m-deep segments at the pier of the Gateway Bridge in Australia and to allow prefabrication of the rebar cages for the webs. This solution has been patented by VSL (Patent pending).
Closure pour casting using the modular form-traveller system at the Gateway Bridge in Australia
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Building modular LNG / LPG tanks using climbform

VSL has taken account of the different LNG tank details adopted worldwide and has developed optimised climbform components for the curved post-tensioned concrete walls used in the tanks.

The inclined starter walls, vertical shell walls, buttresses and the ring beam can all be built without modifications to the standard climbform components.

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Optimised working cycle

VSL’s LNG climbform system is optimised for the interfaces with watertight form ties, climbing cones, PT ducts and vapour barrier plates. The working cycle is optimised by minimising the need for time-consuming adjustment of formwork panels.

Climbing bracket to support ring-beam loads

The VSL climbing bracket takes account of the ring beam loads and avoids time-consuming assembly of additional brackets. The ring-beam lowering device optimises the stripping and increases the safety standards on site due to the components incorporated in its design.

Climbform for PT walls

VSL climbing cones with back anchors are designed for use in LNG tank walls with hollow ducts. This increases the safety of the climbform system.

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