Beyond steel box girders, GNEE offers comprehensive fabrication capabilities for a diverse range of heavy structural steel components utilized in bridge engineering. Our expertise encompasses large-scale steel box columns, steel pipe piling for bridge foundations, steel truss systems, and pedestrian walkway crossbeams.
Should you require specialized bridge steelwork fabrication services, please contact GNEE today!
Steel Box Girders Specification
| Girder Type | Single Box Girder / Multi-Box Girder |
| Span | 30 m – 200 m,or customized |
| Road Width | 8 m – 42 m, or customized |
| Material Grades | Q345qC/D/E, Q370qE, Q420qE, ASTM A709 Gr.50 / Gr.50W, EN 10025 S355J2 / S355NL, JIS SM490 |
| Load Capacity | Designed in compliance with AASHTO HL-93 load standard |
| Surface Treatment | Shot Blasting Sa 2.5,Zinc-rich primer, epoxy intermediate coat & polyurethane topcoat |
| Connection System | Bolt & nut fastener assemblies |
Furthermore, GNEE delivers end-to-end fabrication services, spanning from precision plate profiling to complete girder assembly, while offering a comprehensive portfolio of steel box girder solutions. Our product range includes single-cell, twin-cell, and multi-cell configurations, as well as segmental, horizontally curved, and variable-depth (tapered) box girders. We specialize in the seamless integration of multi-box systems with orthotropic steel decks (OSD). We also offer full customization based on client-provided drawings and specifications. Your inquiries are always welcome.
Single-cell box girder bridge
Twin single-cell box girder bridge
Triple single-cell box girder bridge
Multi-cell box girder bridge
Trapezoidal box girder bridge
Twin multi-cell box girder bridge
Key Advantages of Steel Box Girders
Key Advantages of Steel Box Girders
1.Shallow structural depth: The low-profile section is ideal for sites with stringent vertical clearance constraints, effectively reducing the required length of approach spans.
2.Reduced dead weight: The lighter self-weight of the steelwork minimizes seismic loads on the substructure, significantly enhancing the bridge's overall seismic resilience.
3.Accelerated Construction: Leveraging shop-prefabrication and segmental delivery, the components can be rapidly assembled on-site, ensuring a streamlined installation process and a shorter project schedule.
Key Advantages over Alternative Steel Bridge Designs
1.Superior flexural and torsional rigidity: The high stiffness-to-weight ratio makes these girders ideal for horizontally curved bridges and straight spans subjected to significant eccentric loading.
2.Enclosed hollow section: The hermetically sealed (or fully enclosed) interior prevents the ingress of moisture and corrosive agents, significantly enhancing corrosion resistance and extending the service life of the coating system.
3.Accelerated Erection Efficiency: The design facilitates rapid construction through large-segment integral hoisting or the incremental launching method (ILM), ensuring a shorter project timeline.
4.Clean and streamlined aesthetic: With all internal diaphragms concealed within the box structure, the girder maintains a sleek, unobstructed exterior profile.
Steel Plate Girder Bridge
Steel Truss Girder Bridge
Steel Box Girder Bridge
Production Process of Steel Box Girders
The fabrication of our steel box girders follows an integrated workflow that transitions from sub-component units to a complete spatial structure.
The process initiates with the automated prefabrication of orthotropic steel deck (OSD) units, featuring precision longitudinal U-rib welding. This is followed by the assembly of the internal structural framework, utilizing transverse diaphragms as the core stabilizing nodes. Finally, the box structure is finalized through integrated closure welding and rigorous shop trial assemblies. This systematic approach ensures that each girder segment delivers superior torsional rigidity while strictly adhering to the stringent geometric interface tolerances essential for long-span bridge engineering.
Fabrication Process of Our Steel Box Girders
1. Automated Panel Stiffening
Automated welding of U-ribs to deck plates.
2. Diaphragm Pre-fabrication
CNC cutting and reinforcement of diaphragms.
3. Internal Skeleton Alignment
Setting up the internal structural framework.
4. Segmental Sub-assembly
Fitting and sub-assembly of specific segments.
5. Full Box Enclosure
Final integration and welding of the box section.
6. Trial Assembly & Inspection
Shop trial assembly and final precision checks.
Key Applications of Steel Box Girders
Steel Box Girders are widely utilized in bridge and municipal infrastructure due to their high strength-to-weight ratio, superior torsional rigidity, excellent structural integrity, and accelerated construction cycles. The primary application scenarios and their structural characteristics are outlined below:
1. Urban Viaducts and Interchange Ramps
Application Scenarios: Urban elevated expressways, highway interchange ramps, and small-to-medium span bridges overpassing service roads or railways.
2. Long-Span Bridges (Highway & Railway)
Application Scenarios: Long-span continuous girder bridges; river, maritime, and canyon crossings; and high-load highway and railway infrastructure.
3. Stiffening Girders for Cable-Stayed, Suspension, and Arch Bridges
Application Scenarios: Stiffening girders (main longitudinal girders) or structural components for bridge pylons in long-span cable-stayed, suspension, and arch bridge systems.
4. Pedestrian and Aesthetic Bridges
Application Scenarios: Urban footbridges and architectural landscape bridges.
Steel Box Girder vs I-Girder vs Concrete Girder
Relative performance guidance from structural engineering literature; values are reference, not a substitute for design.
| Aspect | Steel box girder | Steel I-girder | Concrete box girder |
|---|---|---|---|
| Torsional / lateral stability | Closed section, very high torsional stiffness, resists lateral-torsional and distortional buckling | Open section, lower torsional stiffness, needs more bracing and support points | Closed section, good; but formwork-heavy on site |
| Self weight | Carries the same load as concrete while weighing ~50–60% less; OSD deck ~20–30% of a concrete slab | Light | Heavy - can be 2–3× the steel box weight for the same span |
| Curved / horizontal alignment | Excellent, minimal intermediate support required | Moderate; more bracing | Possible but design is heavier |
| Maintenance / durability | Less exposed surface, fewer edges, no exposed bracing - cleaner, lower maintenance | More exposed edges and bracing | Less steel to paint, but concrete maintenance required |
| Erection speed | Factory modules + fast on-site assembly or ILM launching | Fast, segments lifted individually | Slow; cast-in-place cure / heavy precast lifting |
| Best fit | Long spans, curved ramps, marine, 300 m+ feasibility focus | Conventional medium-span bridges | Short–medium spans with cheap local concrete |
Our Customization Services of Steel Box Girders
At GNEE, we don't just manufacture steel components; we provide the core support for complex transportation infrastructure through precision engineering and optimized design. We offer a comprehensive "end-to-end" customization service for steel box girder products.
What Can Be Customized?
We offer deep customization in the following dimensions to meet different bridge spans, load requirements, and environmental conditions:
Geometric Dimensions & Section Shapes
We can custom rectangular, trapezoidal, or streamlined cross-sections based on design requirements.
Material Grade Selection
We are available in various strength grades such as Q355, Q420, and international standards like ASTM A572, S355, etc.
Internal Structural Optimization
We can custom stiffeners (longitudinal & transverse), diaphragms, and manhole positions to enhance torsional stiffness.
Corrosion Protection Systems
We can provide high-standard coatings such as hot-dip galvanizing, epoxy zinc-rich primers, and fluorocarbon paints for marine or industrial environments.
Our Customization Process
Our process ensures precision from the blueprint to on-site installation:
Technical Consultation & Drawing Review
Our engineers analyze your design drawings (CAD/Tekla) to evaluate mechanical feasibility.
01
Detailed Design & BIM Modeling
Utilizing BIM technology for 3D modeling to resolve any potential structural conflicts in advance.
02
Precision Cutting & Fitting
CNC plasma/laser cutting ensures interface tolerances are kept within millimeters.
03
Professional Welding & NDT
Utilizing Submerged Arc Welding (SAW); 100% passing NDT (UT & RT) testing.
04
Pre-assembly & Delivery
Factory pre-assembly of key sections to ensure zero rework on-site.
05
Why Choose Our Customized Steel Box Girders?
Compared to traditional concrete beams, our customized steel box girders offer significant engineering advantages:
Perfect Adaptation to Complex Geometries
Modern bridges often feature steep grades, tight curves, or complex skewed designs. Our customization ensures the fabrication of steel box girders with spatial twists, tapered sections, or variable heights-precision that off-the-shelf components simply cannot match.
01
Optimized Material Efficiency & Weight Reduction
Using Finite Element Analysis (FEA), we customize plate thicknesses based on actual stress distribution-reinforcing high-stress zones while shedding weight in low-stress areas. This reduces steel usage by 10-20%, lowering material costs and easing the load on piers and foundations.
02
Tailored Defense for Specific Environments
Different climates demand different strategies. We customize steel grades (e.g., weathering steel) and coating systems (e.g., heavy-duty anti-corrosion for marine environments). This extends maintenance intervals and slashes long-term operational costs.
03
Modular Design for Zero-Error On-site Assembly
We customize the girder into optimized modular segments based on your site's crane capacity and transport constraints. Each joint is pre-assembled and laser-measured in our factory, ensuring a "perfect fit" on-site that minimizes traffic disruption and construction time.
04
Empowering Unique Architectural Aesthetics
Landscape bridges and urban landmarks require a unique visual language. We transform engineering into art by customizing the curvature, color, and integrated lighting brackets of the girder body.
05
Our Quality Control
From raw material procurement through profiling, welding, and surface preparation, GNEE implements a rigorous suite of inspection and testing protocols to guarantee the superior quality and structural integrity of the steel box girders required for your bridge engineering projects.
Welding Quality Control
1.NDT (Non-Destructive Testing): 100% or sampling UT for all butt welds; RT mandatory for critical tension zones to ensure Class I compliance.
2.Traceability: Inspection reports must specify defect locations. A maximum of two repair attempts is permitted per weld location.
3.WPS Compliance: Real-time monitoring of current, voltage, speed, and preheat/interpass temperatures to ensure strict adherence to qualified WPS/PQR.
Coating & Surface Protection
1.Surface Preparation: Cleanliness verified to Sa 2.5 (ISO 8501-1); anchor profile (roughness) maintained at 50-80μm.
2.DFT (Dry Film Thickness): Measured per 10m²; total thickness must meet design, with individual layer deviations within ±10%.
3.Adhesion: Verified by pull-off tests (≥5MPa) or cross-cut tests; zero delamination allowed.
4.Visual Inspection: Uniform finish free of holidays, pinholes, sags, or peeling; color-matched to approved RAL standards.
Packing & Delivery of Steel Box Girders
1. Surface & Interface Protection
Ends are sealed with waterproof shrink film and desiccants to prevent internal corrosion. Friction surfaces are treated with anti-rust grease, and rubber guards protect the coating edges, ensuring zero damage during long-distance ocean freight.
2. Structural Reinforcement & Anti-distortion
Temporary internal cross-bracing is installed to enhance lateral rigidity during transit and handling. This prevents geometric distortion (diamonding) of the box section, ensuring millimetric precision for on-site fit-up.
3. Flexible Support & Handling Safety
Customized steel saddles with thick rubber padding provide flexible support to avoid metal-to-metal contact. Prominent COG and lifting point markings, along with pre-welded lugs, ensure balanced and safe handling during oversized logistics.
FAQ:
What information do you need to quote a steel box girder?
To give a firm quote we need the minimum: span length and road/marina width, load model (HL-93 or similar), plate thickness and grade, and required surface protection. With just span and width we can give an indicative budget within 24 hours, then a confirmed price once the design drawing is supplied.
Who does the shop/erection detailing, and what does the client receive?
We carry out 3D BIM detailing in Tekla from your design calculation, producing shop/erection drawings, piece-marked cutting/forming schedules and a bill of materials for your approval before fabrication. The detailing cycle is aligned with your project programme.
Are field splices welded or bolted, and how is the method decided?
Large box girders are most often spliced in the field with welded butt joints at the web-and-flange, or with high-strength preloaded bolts where erection speed and on-site inspection matter. The choice depends on site access, crane capacity, weather and your specification.
How do you control flatness and welding deformation of large segments?
Fit-up is anchored by a dedicated assembly jig, controlled SAW heat input in a balanced sequence, and stress-relieving before final closing. Camber and flatness are set and measured before dispatch so field closure stays within tolerance.
Can you accommodate third-party or client inspection during fabrication?
Yes. We welcome client and third-party (TPI) inspectors in the shop, cooperate with hold-point inspections (raw material, welds, dimensions, final fit-up) and issue NDT/UT-RT reports and MTC (EN 10204 3.1).
What site equipment and conditions do the client prepare for erection?
Erection normally needs a crane of adequate rated capacity and a laydown strip, temporary support towers if the design demands, and a levelled working platform sized to our segment modules. We provide the erection scheme and segment lifting points.
