MB modular expansion joint

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.