Concrete

Conventional concrete bridges and prefabricated beams (pre-stressed or post tensioned) are a classical solution for bridging spans of between 6 and 35m but for short span structures this “custom" designed solution is not cost-effective. The cost of the design is disproportionate to the amount of work.

Express Decking is a pre-designed structure that provides a means of bypassing the "custom" solution.

Progress made in France with ultra high performance fibre reinforced concretes (UHPFRC) allows this material to be used economically in the manufacture of industrialised products.

The Express Decking is manufactured from optimised UHPFRC elements, allowing bridges to be delivered and installed quickly and easily and guaranteeing maximum durability for customers.

Specifications

  • For bridging a gap of up to 12 m, comprising a ribbed, and reinforced concrete slab.
  • Using self-supporting UHPFRC formwork.
  • 3.5m wide roadway, combined with pedestrian traffic on 1m wide pavements on either side of the roadway.
  • The structure is an isostatic apron comprising a ribbed, reinforced concrete slab.
  • A spacer at each end of the apron links the ribs to each other, thus providing a crossways stiffening function at the supports.

Materials

UHPFRC box beams and formwork:

The material used for the hollow longitudinal beams, the permanent formwork plates between the ribs and the spacer formwork is UHPFRC with the following characteristics:

  • fck = 150MPa
  • Fctm = -8MPa

The hollow longitudinal ribs are pre-stressed by pre-tensioning with four strands of T13 – 1860 TBR. These elements are heat treated.

Reinforced concrete infill and ribs:

The concrete filling between the spacers and longitudinal ribs is C30/37. The passive steels are type B500B.

Constituent elements in UHPFRC

The pre-stressed, hollow UHPFRC box beam

  • The beam is 25 cm wide and 50 cm tall.
  • It is a pre-stressed UHPFRC element.
  • It acts as formwork for the Express Decking’s ribs and the main beams for the bridge.

The spacer casing

  • This is the formwork for the spacer and the temporary support for the pre-stressed, hollow UHPFRC box beams.
  • It comprises five UHPFRC walls joined together with construction adhesive.
  • The bottom is drilled for linking to the foundations and the side facing the gap is cut out to the dimensions of the box beams.

The spacer casing

Express Decking is constructed in the following stages:

  • Positioning of the spacer casings with their passive reinforcing steels on the foundations.
  • Pouring of the first phase concrete up to the lower edge of the longitudinal boxes.
  • Positioning of the longitudinal UHPFRC box beams and their passive reinforcing steels.
  • Positioning of the horizontal formworks for the infill between the hollow longitudinal box beams.
  • Reinforcement of the infill.
  • Pouring of the second phase concrete into the box beams, the infill is in addition to the rest of the height of the spacer.
  • Fitting of the superstructures, either a weather-proofing and a surface layer, or an UHPFRC surface layer.

Conclusion

  • Simple and innovative design
  • Express Decking results in speed and efficiency of construction
  • The sophistication of UHPFRC as a material, combined with pre-stressing, provides high durability solution - NO MAINTENANCE
Contact us
Contact info@beaverbridges.co.uk or call +44 (0)1743 811811 for advice and further information.
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