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Expansion joints
WBF expansion joint — image 1
WBF expansion joint — image 1

WBF expansion joint

WBF bridge expansion system with intermeshing deck plates.

The WBF series is presented with its structural arrangement, component details and model designation. Selection considers the required deck movement and the interfaces with the bridge deck.

Configuration & selection
Deck-plate and support configuration
Movement and anchorage requirements

For selection, send the design loads, movement requirements and connection drawings. Confirm the model, dimensions and interfaces against your project drawings.

Request product information
Technical information

Applications

Bridge deck joints requiring multidirectional movement, including urban bridges and larger-movement applications.

Key features

  • Independent symmetric modules combine comb plates with elastic support elements.
  • Movement boxes and elastic components accommodate longitudinal, transverse, vertical and torsional movement.
  • Modular construction allows individual units to be accessed for maintenance and replacement.

Technical specifications

Each module includes edge and center comb plates, a movement box, elastic supports, stainless-steel plates and waterproof seals. Specify total movement, horizontal and vertical rotations, skew angle, temperature class and deck recess.

Detailed technical information

WBF modular symmetrical multidirectional comb joints

WBF is presented as a patented family of standard bridge components developed with reference to JT/T 327-2016 and related requirements, for highway, municipal and rail-transit bridges. The design combines features of modular steel joints, ordinary comb joints and unit-type multidirectional comb joints.

A symmetrical, segmented arrangement places one or more centre comb plates between two edge comb plates. Centre-plate width follows the bridge gap, and rotation of elastic elements permits angle changes. The separate centre plate aids installation and replacement. Symmetry simplifies recess preparation and reduces directional differences in vehicle impact.

Design references

JTG D60; JTG 3362-2018; JTG B02-2013; TB 10002.1-2005; TB 10002.2-2005; TB 10002.3-2005; GB 50111-2006; GB 50017-2003; GB 50017-2017; JTG D64-2015; JT/T 327-2016; JT/T 723-2008; JTJ 041-2000; JTG F80/1-2004. These are the supplied catalog’s design-reference editions, covering road/rail bridge design, seismic design, steel structures, expansion joints, construction and quality assessment.

WBF structural advantages and components
Unit assembly and concrete arrangement

Each unit contains two edge comb plates with welded stainless-steel plates, one or more centre plates, two or more movement-support/control systems, two or more elastic elements, two seal-seat plates and two waterproof seals. The unit is configured with one centre plate and two support systems. The unit arrangement facilitates manufacture, transport and installation. Solid concrete placement around the recess differs from hollow arrangements at conventional movement-system ends; symmetrical sides simplify design and casting.

Movement support and elastic elements

The support/control system improves the load path and provides space for elastic elements. These elements connect the centre plate to the control system, allowing multidirectional movement, energy absorption and resistance to rebound. Each centre plate is supported by at least two control systems, each with one or more bolted elastic elements. Independent centre plates span the gap and accommodate three-dimensional girder-end changes through elastic deformation.

Seal-seat plates

The seal-seat plates connect to the upper plates of the elastic elements, linking the individual control systems and centre-plate units. Dedicated grooves make seals easier to install and replace.

The catalog positions the system as combining comb-joint and modular-steel-joint advantages, with cost below conventional multidirectional comb joints of equivalent performance and slightly above modular steel joints. Pricing depends on the selected configuration and project requirements.

Across the bridge, repeated modules contain edge-plate assemblies, centre-plate assemblies, movement boxes, elastic supports, waterproof seals, stainless-steel plates and seal-seat plates.

WBF component diagram and model code
Component key
No. Component
1 Edge comb plate
2 Stainless-steel plate
3 Centre comb plate
4 Elastic element
5 Movement box
6 Waterproof rubber seal
7 Seal-seat plate

The model code lists WBF, movement range in mm, skew angle in degrees (omitted at 0°), horizontal/vertical rotation in rad and suffix F for the cold-resistant version. The normal-temperature version has no suffix.

  • WBF-480-0.02/0.02: normal-temperature joint, 480 mm movement, 0° skew, ±0.02 rad horizontal rotation and ±0.02 rad vertical rotation.
  • WBF-1200-20-0.03/0.02-F: cold-resistant joint, 1200 mm movement, 20° skew, ±0.03 rad horizontal and ±0.02 rad vertical rotation.
WBF performance, durability and maintenance
  1. Modular construction: repeated units have independent functions and simplify design, manufacture, installation and inspection. Dividing the assembly reduces absolute movement demanded of each unit under horizontal and torsional deformation.
  2. Multidirectional movement: elastic elements provide primary movement capability and movement boxes provide supplementary support.
  3. Vibration control: waterproof rubber between steel and concrete, elastic centre-plate support and rounded transitions at comb tips and roots reduce abrupt contact changes and vehicle-induced vibration.
  4. Safety: the symmetrical gap-spanning arrangement divides total movement into two or more smaller movements and reduces the rotation assigned to each side. Vehicle approach is not dependent on a large/small comb-plate orientation.
  5. Durability: low-alloy high-strength steel improves compression and shear resistance; polymer damping elements provide elasticity, strength and fatigue resistance. The surface-level movement system is separated from subsidiary structures, while seals beneath the assembly avoid direct atmospheric exposure.
  6. Noise reduction: intermeshing teeth maintain smoother tyre support, reduce air-pumping effects and split one large impact into smaller transitions. Rubber between steel and concrete reduces rigid contact noise, benefiting urban surroundings.
  7. Construction and maintenance: symmetric recesses and solid concrete placement simplify installation. A damaged module can be removed individually. The product provides local replacement within approximately one lane width, allowing other traffic to continue where the work arrangement permits, and reducing maintenance cost.

The movement mechanism is separated from the concrete and positioned within the girder-end gap. It accommodates longitudinal, transverse, vertical and torsional movement, particularly for large and very large displacement applications.

Expansion joints: selection, materials, transport and storage

MA-C/E/F/L joints use hot-rolled steel profiles and are described for movements up to 80 mm. MB joints comprise edge beams, centre beams, crossbeams and a movement-control mechanism; this overview gives an 80–1200 mm range. Select the movement range for the specified MB model.

Model codes

The code identifies the joint series, profile shape, movement in mm and rubber material: NR = natural rubber; CR = chloroprene rubber. The printed examples describe C-profile 60 mm CR, F-profile 80 mm NR and MZL modular 480 mm NR joints.

Design and manufacturing conditions
  • The catalog cites JT/T 327-2016 and its printed vehicle load designation.
  • Profiled steel: 16Mn bridge steel, tensile strength at least 480 MPa and allowable bending stress at least 210 MPa.
  • Supporting crossbeams: 16Mn or grade 45 steel, allowable bending stress at least 210 MPa.
  • Other steel components: at least Q235 strength.
  • CR rubber temperature range: −25°C to +60°C. NR or EPDM: −40°C to +60°C.

The modular arrangement separates the load-carrying structure from the movement-control system so that load transfer and uniform movement do not interfere with each other.

Selecting movement capacity

Calculate bridge movement, allow an appropriate reserve and consider the available gap and anchorage at girder/slab ends. Supply the bridge cross-section, crossfall, footway, safety strip and barrier positions/dimensions; construction timing and installation-temperature range; and any special requirements. If no setting value is supplied, the factory presets the joint at half its rated maximum movement, citing JT/T 327-2016.

Transport and storage

Joints are assembled to the design before transport. Where transport length or other restrictions prevent delivery as one piece, sectional manufacture is possible. Store near the installation location on supports at least 300 mm above ground.

Expansion-joint installation and skew arrangements

  1. Install preferably after road surfacing. Check recess width/depth and embedded reinforcement against the installation requirements.
  2. Remove all dirt, dust and unnecessary material from the recess.
  3. Check the gaps between beams against the installation temperature. If adjustment is needed, do it under the manufacturer’s technical guidance, then refit the installation clamps.
  4. Using the adjacent asphalt surface as the elevation datum, lift the joint into the recess and set its top level and longitudinal profile to the road.
  5. Check position both along and across the joint; resolve any interfering embedded reinforcement while maintaining the design alignment.
  6. Weld the anchors on one side to the embedded reinforcement, initially at alternate positions, then do the other side. Once securely fixed, remove the clamps and complete all remaining anchor welds. Do not weld arbitrarily on centre or edge beams.
  7. For sectional installation, align and weld the factory-prepared profile splices before completing the anchorage sequence.
  8. Fit tight formwork at girder ends to prevent mortar entering movement-control boxes or the end gap.
  9. Recheck formwork and clean the recess. Place and compact concrete with strength at least equal to the adjacent structural concrete. Keep the joint top clean.
Skew installation

Where the crossing direction is oblique, anchor reinforcement and movement-control boxes may be arranged at an angle to the edge beam. These installation instructions cover 0–80 mm joints and MB 160–400 mm modular joints. The angle follows the bridge skew. Drawing notation: h = recess depth; b = recess width; α = angle between anchor reinforcement and edge beam. Select the MA-C, MA-F or MA-L arrangement to suit the actual recess, or provide special drawings for design. The 160 mm section refers to the wider 160–1200 mm installation drawing series.