In bridge construction, formwork selection is far more than just choosing a temporary "mold" for concrete. It is a critical decision that directly impacts the project's overall cost, structural quality, and construction schedule. Focusing solely on the initial unit price of formwork can be shortsighted, often leading to higher total costs.

This guide, drawing on Boyoun's extensive project experience, provides a clear and practical strategy for selecting formwork for different bridge types, helping you avoid common pitfalls.

1. Why "Selecting Right" is Crucial

Before diving into specific solutions, let's clarify a key point: Why is selecting the correct formwork so crucial for bridge projects? Many clients initially focus only on the unit price of formwork, overlooking subsequent impacts, and end up at a disadvantage.

l Saves Time: The right formwork directly shortens the construction cycle. For example, for a simply supported beam bridge with a 20-meter span, using modular steel formwork compared to timber formwork can shorten the construction period by 5-7 days per bridge. If a project involves 10 bridges, the overall project can be completed over a month earlier, reducing the risk of penalties for delays.

l Ensures Quality: Formwork is the "mold" for concrete shaping. If the formwork precision is insufficient, the cast beam might have dimensional deviations or surface honeycombing. Subsequent repairs not only cost money but can also affect the bridge's structural safety. We previously encountered a client who used non-standard timber formwork, resulting in beam surface flatness errors exceeding 8mm. This ultimately cost over 20,000 RMB for grinding and repairs, delaying acceptance.

l Controls Cost: Seemingly cheap formwork may hide high costs. For instance, ordinary timber formwork can typically be reused 3-5 times, whereas high-quality modular steel formwork can be reused 15-20 times. Calculating for a 10-bridge project, the single-use cost of steel formwork can be over 40% lower than timber formwork. Always prioritize these three values when selecting formwork.

2. Tailored Solutions: Formwork Selection for Four Bridge Types

2.1  Girder Bridges

Beam Bridges are the most common type, ranging from small bridges on rural roads to large bridges over rivers in cities. Their core characteristic is that the main girders primarily resist bending moments, and construction techniques are relatively mature. Therefore, formwork selection mainly adapts to the span length. Based on our project experience, the core principle is to choose formwork based on "Span Length" and "Construction Method". Let's look at the specifics.

（1）Small and Medium Span Beam Bridges (Span ≤ 20m, e.g., township roads, park access roads) 

Recommended Formwork: Modular Steel Formwork (Prefer Q235 or Q345 steel grade – also a main product of Boyoun Heavy Industry)

Why Choose It: Firstly, fast assembly/disassembly: 2 workers can assemble 100㎡ of formwork in half a day, 3 times more efficient than timber formwork, significantly reducing on-site construction time. Secondly, high precision: joint error ≤1mm, resulting in beam surfaces that don't require secondary plastering, saving subsequent process costs. Finally, high durability: can be reused over 15 times with normal maintenance, making it more economical in the long run.

Addressing Client Pain Points: Many clients worry about the heavy weight and difficult transport of modular steel formwork. Boyoun Heavy Industry has a mature solution: we design the formwork in segments based on transport vehicle dimensions, with single piece weight controlled between 50-80kg. This allows transport by ordinary trucks, eliminating the need for specialized large cranes and reducing transport costs – a design praised by many clients.

（2）Large Span Beam Bridges (Span 20-70m, e.g., urban continuous beam bridges over rivers)

Recommended Formwork: Form Traveler (Must be custom-designed according to the girder cross-section. Boyoun Heavy Industry offers full-process customization services).

Key Considerations: These bridges mostly use the cantilever casting method. The "stability" and "adjustability" of the form traveler are crucial. Based on our experience: first, the load-bearing structure of the traveler must withstand 1.2 times the design load to prevent deformation during concreting, which we ensure through rigorous stress calculations; second, the formwork must be equipped with a micro-adjustment system, allowing position adjustments within a ±50mm range to handle alignment deviations during construction, ensuring the girder alignment meets design requirements.

Our Technical Advantage: Boyoun Heavy Industry's form travelers use a rhombic truss structure, which is 20% lighter than traditional triangular structures but has 15% higher load-bearing capacity, facilitating transport and installation. They are also equipped with a fully automatic hydraulic adjustment system, allowing operators to adjust the formwork position from a ground control console, eliminating the need for work high above the ground – enhancing both safety and efficiency. This technology has been applied in multiple large-span projects.

2.2 Arch Bridges

Having covered beam bridges, let's now discuss arch bridges, which have a distinct load-bearing mechanism. Unlike beam bridges relying mainly on girder bending, arch bridges transfer loads primarily through axial compression in the arch rib. Furthermore, many arch bridges are used in scenic areas or urban landscapes, requiring both structural safety and aesthetic appeal. Thus, formwork selection differs significantly from beam bridges. Based on Boyoun Heavy Industry's service experience, focus on "arc precision" and "surface finish" when selecting formwork. We'll cover small and large span categories.

（1）Small Arch Bridges (Span ≤ 30m, e.g., scenic landscape bridges, rural stone arch bridges)

Recommended Formwork: Full Scaffolding + Custom Timber Formwork / Bamboo Plywood Formwork

Core Requirements: First, scaffolding must be stable because arch bridge construction imposes significant horizontal thrust on the supports. We typically densify the scaffold upright spacing to 0.8m×0.8m and add anti-sliding devices at the base to ensure construction safety. Second, the formwork must accurately represent the arch curve. For instance, if a client wants a semi-circular arch, the formwork's arc error must not exceed 3mm; otherwise, the cast arch ring may deform, affecting appearance and structure.

Cost-Saving Tip: If appearance requirements are low (e.g., rural stone arch bridges), ordinary timber formwork can be used. For scenic landscape bridges, bamboo plywood formwork is recommended as it offers a smoother surface, often eliminating the need for post-casting painting, saving on later decoration costs. We advise on the most suitable type based on client budget and needs.

(2)Large Span Arch Bridges (Span 30-170m, e.g., mountain highway arch bridges) Recommended Formwork: Precast Segment Formwork + Cantilever Casting Form Traveler (Selected based on construction method. Boyoun Heavy Industry can adapt to different process requirements).

Addressing Challenges: The biggest issues for large span arch bridges in mountainous areas are difficult transport and limited construction space. To address this, based on our project experience, Boyoun Heavy Industry's precast formwork uses a "split design." For example, the arch rib formwork is divided into 3-4 segments, each weighing under 3 tons, allowing transport to mountain sites using medium-sized trucks, solving transport issues. For on-site assembly, specialized positioning jigs are provided to ensure splicing errors ≤2mm, guaranteeing arch rib construction precision.

2.3 Cable-Stayed Bridges

While arch bridges rely on arch rib compression, cable-stayed bridges have a more complex structure with three core load-bearing components: the girder, cables, and pylon. Loads are transferred to the pylon via the stay cables. This structure gives them greater spanning capacity than beam bridges and small arch bridges, often used for medium-span scenarios like urban river or lake crossings. Due to this complexity, the formwork approach cannot focus on a single component like the previous types. Instead, it requires separate designs for the girder and pylon, ensuring smooth integration between them. From our project service perspective, the formwork plan must be "designed separately but coordinated," otherwise, workflow connection issues can arise, affecting the overall schedule. Let's examine the formwork solutions for the girder and pylon separately.

（1）Girder Construction: Divided into "Precast Segment" and "Cantilever Casting"

 Precast Segment Method (Suitable for spans 80-150m, e.g., urban expressway cable-stayed bridges): Recommend "High-Precision Precast Formwork." The mating surfaces of Boyoun Heavy Industry's precast formwork undergo CNC milling, achieving flatness errors ≤0.5mm, ensuring precast segments fit tightly together during assembly, reducing on-site adjustment time, and improving construction efficiency.

Cantilever Casting Method (Suitable for spans 150-200m, e.g., river-crossing cable-stayed bridges): Use a "Multi-function Form Traveler." Beyond standard load-bearing and adjustment functions, it incorporates pre-set openings for stay cables based on client needs. The position error of these openings must not exceed 1mm; otherwise, cable installation deviations occur. We ensure precise opening placement through precision processing, guaranteeing smooth subsequent processes.  

（2）Pylon Construction: Climbing Form vs. Jump Form–How to Choose?

Climbing Form (Suitable for pylons ≥50m high, e.g., sea-crossing cable-stayed bridges): Advantage is high automation; it climbs automatically as concrete is poured, eliminating manual disassembly/reassembly, saving about 30% on labor costs. However, pay attention to the stability of the hydraulic system. Boyoun Heavy Industry's climbing forms feature dual hydraulic pumps; if one fails, the other activates immediately, preventing work stoppages – a key safety feature we provide.

Jump Form (Suitable for pylons ≤50m high, e.g., urban cable-stayed bridges): Costs about 15% less than climbing forms but requires manual layer-by-layer formwork jumping. Suitable for sites with ample construction space. To ensure precision, we add positioning pins at the jump form connections, ensuring verticality error per layer ≤1mm, preventing pylon tilt, and safeguarding pylon structural safety.

2.4 Suspension Bridges

If cable-stayed bridges are the preferred choice for medium spans, suspension bridges are the "kings" of super-large spans. Many bridges crossing seas or large gorges are suspension bridges. They rely on main cables and anchorages to withstand enormous loads, achieving spans of hundreds or even thousands of meters. This massive scale demands higher formwork strength and precision than the previous three bridge types, especially for the stiffening girder and anchorage – key components directly determining the bridge's safety. Based on Boyoun Heavy Industry's project experience, the formwork plan focuses on "Stiffening Girder Precast Precision" and "Anchorage Concreting Stability." Let's detail these.

（1）Stiffening Girder Formwork: Steel Box Girder vs. Concrete Girder – Big Differences

l Steel Box Girder (Suitable for large span suspension bridges, e.g., sea-crossing): Formwork is primarily used in the factory precast stage to ensure welding precision. Boyoun Heavy Industry's steel box girder formwork includes dedicated welding positioning jigs, controlling welding deformation within 2mm, complying with standards like GB/T 14684-2022, ensuring girder quality meets standards.

l Concrete Girder (Suitable for medium span suspension bridges, e.g., mountain suspension bridges): Can reference the cantilever casting formwork for cable-stayed bridge girders, but must enhance wind resistance. For example, adding wind shields on both sides to cope with strong mountain winds, preventing concrete dispersal during pouring – an optimization based on our experience in mountainous environments.

（2）Anchorage Formwork: Must Use "Large Modular Steel Formwork"

 The anchorage is the "foundation" of a suspension bridge, bearing the immense tension from the main cables. Concrete pour volumes are often thousands or even tens of thousands of cubic meters. It requires large modular steel formwork with high strength and stiffness. Boyoun Heavy Industry's modular steel formwork uses 10mm thick steel plates reinforced with back-to-back channels, capable of withstanding 50kN/m² lateral pressure. Deformation during pouring is ≤3mm, ensuring anchorage casting quality and providing foundational safety assurance for the suspension bridge.

3. 3-Step Decision Method for Choosing Formwork

From the girder bending in beam bridges, to arch rib compression in arch bridges, to the coordination of girder, cable, and pylon in cable-stayed bridges, and the main cable-anchorage load-bearing in suspension bridges, structural differences dictate the formwork approach. Having covered these solutions, based on Boyoun Heavy Industry's service experience, we conclude with a simple and practical "3-Step Decision Method" to help you quickly determine the right formwork plan:

Step 1: Define the Scenario: Clarify the bridge type, span length, and construction method (Precast / Cast-in-place). This is the foundation for selecting formwork and our primary basis for developing client solutions.
Step 2: Identify Needs: Prioritize core requirements. Is it saving time? Ensuring quality? Or controlling cost? For example, choose steel formwork to save time; choose timber formwork for budget control and small spans. We recommend the most suitable product based on the client's core needs.
Step 3: Check Credentials: When selecting a formwork manufacturer, check for specialbridge formwork production qualifications and the availability of mature technical solutions. Boyoun Heavy Industry possesses complete production credentials and rich project experience, providing clients with reliable products and services, avoiding the risk of products from small workshops with no support if problems arise later. 

Conclusion

Selecting the right formwork is a critical techno-economic decision. Boyoun Heavy Industry, as a professional bridge formwork solution provider, offers not only high-quality products but also full life-cycle technical consultation to help your project achieve cost-effectiveness and timely success.

Do you have a specific project requiring a formwork solution? Contact our expert team today for a personalized consultation and a customized proposal.