In the world of large-scale infrastructure, speed, safety, and efficiency are paramount. For the construction of long, multi-span viaducts, one technology stands out for its ability to revolutionize the entire process: the Movable Scaffolding System (MSS).

An MSS is essentially a “bridge factory on wheels.” It’s a self-contained, self-launching system that allows for entire bridge spans to be cast in place without relying on traditional, ground-based scaffolding. By industrializing the construction site, this technology enables projects to be completed faster, more safely, and with a higher degree of quality control than ever before.

Key features include:

• Full-Span Construction: An entire bridge span (the section between two piers) is cast in a single, continuous operation.
• Self-Launching: After a span is complete, the system hydraulically moves itself forward to the next set of piers to repeat the cycle.
• Two Main Types: Systems are either Overhead (where the main support structure is above the bridge deck) or Underslung (where it is positioned below).

The On-Site Construction Cycle: A Step-by-Step Look

Unlike a generic project plan, the true efficiency of an MSS is in its physical, on-site, and highly repetitive weekly cycle.

1. Positioning the System: The MSS is launched forward from the completed section of the bridge and securely positioned onto the next set of piers.
2. Formwork and Reinforcement: The formwork (the mold for the concrete) is set up, and the steel reinforcement cage is assembled inside it. This is all done on the stable platform of the MSS.
3. Concrete Pour and Curing: The full bridge span is cast with concrete in one continuous pour. The concrete is then left to cure and gain the required strength, supported entirely by the MSS.
4. Post-Tensioning: Once cured, high-strength steel tendons are run through the concrete and tensioned. This process, known as post-tensioning, gives the bridge span its structural integrity.
5. Launching Forward: The formwork is lowered, and the entire MSS system launches itself forward to the next piers to begin the cycle all over again.

The Core Advantages: How MSS Boosts Efficiency

The primary reason for using an MSS is to achieve a level of efficiency that is impossible with traditional methods.

• Unmatched Speed: The repetitive, industrialized cycle allows a well-managed team to complete a full 40–50 meter span every 7 to 10 days. This predictable speed is critical for meeting tight project deadlines.
• Significant Cost Savings: By eliminating the need for massive, ground-up scaffolding for every span, an MSS dramatically reduces material and labor costs. Its high level of mechanization also means smaller, more specialized crews are needed.
• Enhanced Safety and Quality: The MSS provides a single, integrated, and stable working platform. This controlled environment significantly improves worker safety compared to scattered scaffolding and leads to a more consistent, higher-quality concrete structure.
• Minimal Ground-Level Impact: As a “top-down” construction method, an MSS has a very small footprint on the ground. This is a crucial advantage when building over water, sensitive ecosystems, or active roadways and railways.

Ideal Applications: When is MSS the Best Choice?

While powerful, an MSS is a specialized piece of equipment. It is the most suitable and efficient method for projects with the following characteristics:

• Long, Multi-Span Viaducts: The system’s main advantage is its repetitive cycle, making it perfect for bridges and viaducts with many similar spans.
• Projects in Difficult Terrain: It is the ideal solution for building bridges high over deep valleys, wide rivers, or other areas where building scaffolding from the ground would be impractical or impossible.
• Construction Over Active Areas: Its ability to work from above makes it the preferred choice for building over busy highways, railways, or other infrastructure that cannot be shut down.

How MSS Technology is Shaping the Future of Bridge Construction

MSS technology is a key enabler for the rapid and sustainable development of the long-span viaducts and highway networks that modern economies demand. By turning the construction site into a mobile production line, it is pushing the industry toward a future that is faster, safer, less disruptive, and more integrated with digital tools like Building Information Modeling (BIM).

The repetitive cycle also opens the door for future automation, further solidifying the MSS as a cornerstone of modern bridge engineering.

Strukturas has a perfect team for your bridge. If you wish to use most benefits of MSS – let’s chat.

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Formwork, Operations and Logistics in Formtraveller 

The efficiency of a Formtraveller depends heavily on how the formwork is designed and handled, and how site operations and logistics are planned. This includes panel dimensions, formwork surfaces, internal formwork launching, crew size, launching speed and workshop pre-assembly.

 

Internal and external formwork: configuration and handling

In typical applications, the external and internal formwork panels have a length of about 5.8 m, assuming a maximum segment length of 5 m in the concrete deck.

Internal and external panels are connected using threaded ties, such as Dywidag bars, passing through the deck webs. This creates a closed, stable formwork box that can carry fresh concrete and construction loads.

The internal formwork in Formtravellers is usually launched manually from one segment to the next:

• Chain tackles are commonly used to move the internal formwork along rails.
  
• Hydraulic cylinders can also be adopted, but the standard solution in many projects remains manual.
  
• The rails on which the internal formwork rests are launched together with the main structure of the Formtraveller.
  

As mentioned earlier, the position of internal diaphragms must allow the internal formwork to pass. If diaphragms are too close to the front of the segment, the internal formwork may need to be dismantled behind the diaphragm.

 

Formwork surfaces and materials

The most common formwork surface used in Formtraveller Systems is:

• Phenolic plywood, usually 21 mm thick.
  

Steel formwork surfaces are technically possible but rarely preferred:

• Rebuilding steel formwork for future projects is costly.
  
• For typical segment lengths and project sizes, plywood offers a better economic balance.
  

The usual arrangement is:

• Plywood sheets are screwed to timber sections.
  
• Timber sections are bolted to the steel ribs of the formwork structure.
  
• Parts of the internal and external web formwork are often made using wooden beams.
  

If the number of segments is very high, the phenolic plywood can be replaced during the life of the Formtraveller, while the underlying steel structure remains reusable.

 

Handling reinforcement: limits and special solutions

As a rule:

• Overhead Formtraveller do not normally allow the transport of pre-assembled reinforcement cages on the system itself.
  

However, in some specific projects where:

• The deck webs are vertical or nearly vertical, and
  
• Pre-assembled web rebar panels are desired,
  

it may be possible to develop special transport rails integrated into the Formtraveller. In such cases:

• A crane installs the pre-assembled web reinforcement panel.
  
• The load is then transferred from the crane to the special rails of the Formtraveller.
  

These are project-specific solutions, not the standard configuration.

 

Crew size, launching speed and construction cycle

To operate a Formtraveller– including:

• Opening the formwork
  
• Launching from one segment to the next
  
• Closing the formwork
  
• Introducing camber
  
• Preparing the formwork for reinforcement
  
• Concreting the segment
  

– a dedicated crew is required. 

The exact crew size depends on the segment weight, deck width and the target construction cycle, but in general:

• A team of 8 to 10 people per pair of Formtravellers is typical.
  

Regarding relocation speed:

• The normal launching speed of a Formtraveller is around 10 m per hour.
  
• Increasing the launching speed does not make practical sense, since the maximum segment length is only about 5 m. The marginal time savings are minimal, and the risks associated with higher movement speeds increase.
  

The typical construction cycle for a pair of segments using Formtravellers is approximately:

• 1 week per pair of segments,
  assuming standard times for reinforcement assembly, prestressing operations, concrete curing, and formwork operations.
  
  

Workshop pre-assembly, transport and on-site planning

During the original manufacture of a Formtraveller System:

• The steel structure is usually partially pre-assembled in the workshop.
  
• All components are marked with references, indicating their position in the final assembly.
  

For transport:

• Parts are designed to fit in 40-foot containers or on TIR truck platforms.
  

On site, careful planning of assembly and dismantling is essential:

• Correct definition of lifting points for sub-assemblies.
  
• Ensuring that the centre of gravity of each assembly stage remains within safe limits.
  
• Guaranteeing suitable access for cranes and transport equipment.
  

Accurate weights of all parts must be known:

• Typically derived from 3D models or detailed 2D drawings.
  
• If there is any uncertainty, scales can be used to confirm the component weights.
  
  

Design Criteria Document: selecting the right Formtraveller 

To evaluate whether a given Formtraveller is suitable for a specific bridge deck, it is essential to prepare a Design Criteria Document. This document must clearly define at least:

• Loads from the concrete segments and launching situation
  
• Safety factors
  
• Wind speeds:
  
  • During launching
    
  • During concreting
    
  • Under storm conditions
    
• Materials and steel grades
  
• Maximum span
  
• Live loads and other construction loads
  

The cost and site performance of a Formtraveller depend strongly on these definitions. A well-prepared Design Criteria Document is therefore the key technical basis for:

• Deciding whether an existing system can be reused or adapted, or
  
• Designing a new system optimised for the specific project.
  

In most successful cantilever projects, the Formtraveller is not an afterthought but an integral part of the initial design strategy for the bridge.

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Bridge construction has evolved dramatically over the past few decades. Among the most efficient technologies for cast-in-situ segmental bridge construction are Form Travellers (FTs) and Movable Scaffolding Systems (MSS).

Both systems enable builders to construct long-span bridges without extensive falsework or ground support. However, each has unique advantages, limitations, and ideal use cases. In this article, we’ll explore the key differences between Form Travellers and Movable Scaffolding Systems, helping you determine which is best suited for your next bridge project.

What Is a Form Traveller (FT)?

A Form Traveller is a specialized structural system used to cast bridge segments in place — typically in balanced cantilever construction. It allows engineers to build a bridge span segment by segment, extending out from a pier on both sides to maintain equilibrium.

Types of Form Travellers

There are two main types:

• Overhead Form Traveller: Supported from above the deck, ideal for deep valleys or bridges over water.
• Underslung Form Traveller: Suspended below the deck, used when there is sufficient space beneath the structure.

How It Works

The traveller is positioned at the end of the previously cast segment. After reinforcement, formwork, and concreting are completed, the new segment is cured and post-tensioned. The form traveller is then moved forward to the next position — repeating the cycle until the span is complete.

Advantages of Form Travellers

1. Minimal Ground Interference

Form travellers are entirely supported by the completed bridge structure itself, eliminating the need for ground-based falsework or scaffolding.

This makes them ideal for bridge construction over challenging terrains such as rivers, deep valleys, highways, and railways, where erecting temporary supports would be costly, dangerous, or even impossible.

By suspending operations above ground, contractors can work safely and continuously without disrupting the environment or traffic below.

2. High Precision and Geometric Control

Each segment constructed using a form traveller is aligned directly from the previous one, ensuring millimeter-level accuracy in deck geometry, slope, and alignment.

This precision is particularly important for long-span balanced cantilever bridges, where even small cumulative errors could result in significant misalignment.

Modern form traveller systems are equipped with hydraulic adjustment and monitoring systems, allowing engineers to maintain perfect geometry throughout construction.

3. Adaptability to Complex Bridge Designs

One of the strongest advantages of form travellers is their flexibility. They can easily adapt to variable spans, curved alignments, varying deck depths, and asymmetric cross-sections – features commonly found in modern architectural bridge designs.

Because the system is modular, it can be adjusted or modified for different segment lengths or shapes, making it suitable for architecturally complex or topographically challenging bridge projects.

4. Reduced Environmental Impact

Since form travellers do not require temporary supports or extensive site preparation, they significantly minimize ecological disturbance.

There is no need for foundation works in rivers or forests, which helps preserve wildlife habitats and natural landscapes.

This makes the method particularly favored in environmentally sensitive areas where traditional falsework would not be permitted.

5. Safety and Accessibility

Form travellers provide a stable and controlled working platform directly attached to the bridge, reducing risks associated with working at height or on unstable ground.

Engineers and workers can perform concreting, post-tensioning, and inspection operations in a secure environment with integrated walkways and access systems.

This contributes to improved safety performance and reduced downtime due to weather or ground conditions.

6. Long-Term Reusability

A well-designed form traveller can be reused across multiple spans or projects, which makes it a cost-efficient investment for companies specializing in segmental bridge construction.

The modular steel structure allows for quick assembly, disassembly, and transportation between job sites, enhancing operational efficiency over time.

Limitations of Form Travellers

1. Slower Construction Rate Compared to MSS

While form travellers offer exceptional flexibility, their cycle time per segment is typically longer than that of movable scaffolding systems (MSS).

Each segment must be individually set, reinforced, concreted, cured, and post-tensioned before the traveller can be advanced to the next position.

This makes the process less efficient for long, repetitive viaducts where uniform spans could be cast faster using span-by-span methods.

2. Higher Skill, Labor, and Equipment Requirements

Operating a form traveller demands specialized engineering expertise.

Precise alignment, load balancing, and structural monitoring are critical to ensure safety and quality.

Crews must be experienced in post-tensioning, segmental casting, and geometry control, which increases labor costs and training requirements.

Additionally, form travellers rely on advanced hydraulic and lifting equipment, adding to both capital and maintenance expenses.

3. Not Ideal for Low-Level or Easily Accessible Bridges

For bridges constructed close to the ground or in areas with easy site access, using form travellers is often unnecessary and uneconomical.

In such cases, conventional scaffolding or movable scaffolding systems (MSS) offer faster setup, simpler logistics, and lower overall costs.

Form travellers are most cost-effective when ground support is impractical or when the bridge spans are too long for traditional falsework methods.

4. Higher Initial Setup Time

The initial assembly, calibration, and load testing of a form traveller require considerable preparation.

Before casting begins, the system must be precisely aligned with the pier segment, balance loads must be verified, and safety systems must be tested.

While this setup ensures accuracy and safety, it also extends the pre-construction phase, which can affect project timelines.

5. Weight and Stability Constraints

Form travellers carry significant loads from both the fresh concrete and the equipment.

As a result, the pier and segment structure must be strong enough to support these loads during cantilevering.

For lighter or slender piers, additional temporary stabilization may be necessary — slightly reducing the overall efficiency advantage.

What Is a Movable Scaffolding System (MSS)?

A Movable Scaffolding System, often referred to as a Launching Girder, is an advanced construction method used for span-by-span cast-in-situ bridges. Instead of building segments one by one from a pier, the MSS supports the entire span during concreting.

Types of MSS

• Overhead MSS: The truss structure is positioned above the bridge deck.
• Underslung MSS: The truss structure is below the deck, used when overhead clearance is limited.

How It Works

The MSS is positioned between two piers. Once the formwork and reinforcement are ready, the entire span is cast in place. After curing and post-tensioning, the system is moved (or “launched”) to the next span. This method is ideal for repetitive spans of similar geometry.

Advantages of Movable Scaffolding Systems (MSS)

1. High Construction Speed

The Movable Scaffolding System (MSS) is designed for rapid, span-by-span construction.

Unlike form travellers that cast one short segment at a time, the MSS supports and casts an entire bridge span in a single cycle. Once the concrete has gained sufficient strength and post-tensioning is complete, the entire system is “launched” or moved forward to the next span.

This cyclical workflow significantly reduces construction time, making the MSS ideal for large-scale infrastructure projects such as expressways, metro viaducts, and high-speed rail bridges where many similar spans are required.

2. Efficiency for Repetitive and Standardized Designs

MSS technology is most efficient in projects that have repetitive span lengths and uniform geometry.

When bridge spans, pier heights, and deck shapes remain consistent, the system can operate in a steady rhythm that minimizes manual adjustments.

This efficiency not only saves time but also reduces material waste and formwork errors.

For long viaducts or elevated highways with repetitive spans, MSS is often the most cost-effective construction method available.

3. Excellent Safety and Working Platform

One of the major advantages of MSS is that it provides a secure and self-contained working platform.

Workers can complete all tasks such as formwork installation, reinforcement, concreting, and inspection safely within the structure itself.

Integrated walkways, railings, and working decks ensure excellent accessibility and safety, even when operating at significant heights.

This controlled working environment minimizes risks related to wind, unstable ground, or traffic underneath the bridge.

4. Reduced Crane Dependency

The MSS carries its own formwork, reinforcement, and concreting systems, which reduces the need for cranes during bridge construction.

Most operations are performed directly on the system, allowing continuous workflow even when crane access is limited or costly.

This feature is particularly valuable in urban environments or over busy roads, where lifting operations are restricted.

5. Consistent Quality and Alignment

Since each span is cast under identical conditions, the MSS ensures high geometric accuracy and surface quality across the entire structure.

Automated formwork adjustment systems maintain the correct deck profile and alignment, resulting in consistent appearance and performance.

This uniformity is especially important for transport infrastructure where smoothness and symmetry affect both aesthetics and durability.

6. Cost Efficiency for Large Projects

Although the initial investment in MSS equipment is significant, the cost per span decreases quickly when the number of spans is large.

For long viaducts with hundreds of spans, the amortized cost of the system makes it an economically efficient option, especially when combined with faster construction and reduced labor needs.

Limitations of Movable Scaffolding Systems (MSS)

1. Limited Flexibility for Variable or Curved Spans

MSS performs best on bridges with straight alignments and consistent span lengths.

If the spans vary in length or curvature, the system must be heavily modified, which reduces efficiency and increases setup time.

Bridges with complex geometry or asymmetrical designs often require custom adjustments that make the MSS less practical.

2. Heavy and Complex Setup

Movable scaffolding systems are large and mechanically complex.

They include heavy steel trusses, hydraulic lifting systems, and built-in formwork, all of which require specialized assembly and calibration.

Initial setup and testing for the first span can take several weeks, which makes MSS unsuitable for short bridges or one-time projects where the cost and time of assembly outweigh the benefits.

3. High Load Demands on Piers and Foundations

During concreting, the MSS together with fresh concrete applies very high temporary loads on the piers and foundations.

These loads can exceed the bridge’s service loads, meaning that the substructure must be designed to resist both permanent and construction-phase stresses.

This may increase pier size, reinforcement requirements, and overall construction cost.

4. High Initial Investment

The MSS requires a large upfront investment for design, fabrication, and installation.

It involves specialized hydraulic and launching systems as well as strong truss structures.

For small-scale or unique projects, this cost may not be justified.

However, for long linear projects such as highways and metro viaducts, the system becomes highly economical after repeated use.

5. Limited Suitability in Confined or Steep Terrain

The MSS requires ample space to move between spans.

In mountainous areas, curved alignments, or tight urban zones, it can be difficult to reposition or stabilize the system safely.

In such conditions, Form Travellers or precast methods are often more flexible and practical.

Form Traveller vs. Movable Scaffolding System: A Detailed Comparison

Feature	Form Traveller (FT)	Movable Scaffolding System (MSS)
Construction method	Segment-by-segment (balanced cantilever)	Span-by-span (continuous casting)
Span length	50–250 m	25–70 m
Speed	Slower but more flexible	Faster for repetitive spans
Flexibility	High — suitable for curves and variable spans	Limited — best for uniform spans
Ground clearance requirement	None (works over deep valleys or water)	Requires moderate clearance
Structural weight	Relatively light	Heavy steel structure
Typical applications	Cable-stayed bridges, high viaducts, crossings over obstacles	Elevated highways, metro viaducts, long repetitive bridges
Environmental impact	Minimal (no ground falsework)	Moderate (depends on site setup)
Initial investment	Lower	Higher, but faster payback on large projects

Choosing the Right System for Your Project

The choice between a Form Traveller and a Movable Scaffolding System depends on several key factors:

1. Bridge Geometry:
   • If your project involves curved alignments or variable spans, a Form Traveller is more practical.
   • For straight, repetitive spans, the MSS offers faster cycle times.
2. Site Conditions:
   • Form Travellers excel in areas with limited ground access (deep valleys, rivers, railways).
   • MSS requires space for movement and assembly, so it’s better suited for open terrain.
3. Budget and Timeline:
   • MSS involves higher upfront costs but pays off for large-scale projects with many spans.
   • Form Travellers are more cost-effective for shorter bridges or complex geometries.
4. Environmental Impact:
   • Form Travellers are ideal for sensitive ecological zones where minimizing ground disturbance is crucial.

Real-World Examples

• Form Traveller Use: on the link you can find many projects that we have completed during the years and used form travellers to construct various bridges.
• MSS Use: on the link you will find many bridges that we helped to build with MSS for repetitive spans, ensuring efficiency and uniformity.

Conclusion

Both Form Travellers and Movable Scaffolding Systems have revolutionized modern bridge construction. The Form Traveller stands out for its flexibility and precision in complex, high-altitude, or environmentally sensitive projects. Meanwhile, the Movable Scaffolding System shines in high-volume, repetitive-span infrastructure where speed and efficiency are paramount.

The best solution depends on your project’s geometry, environment, and timeline – not just the technology itself.

STRUKTURAS
WE MAKE IT SIMPLE!