The railway bypass in Mechelen is a project with a large number of bridges. Several building methods where applied to integrate them optimally in the modernized station area.

The construction of the railway bypass of approx. 3,5 km is essential to enable a speed increase of the passing international trains from 100 to 160 km/h at the railway station of Mechelen. The project includes the construction of several elevations and structural works, such as a railway viaduct and two steel bridges: one over the canal Leuven-Dijle and another over the Dijle river.

Given their particular characteristics, the THV STAMechelen has consigned the production of the largest prefabricated prestressed elements in this project to Ergon. At the end of last year, 12 preflex beams of 42 m long were already delivered, but the production of Z-shaped beams of 2.85 m high, 1 m wide and 43 m long became the showpiece. In all, 4 beams of this kind were produced at the Ergon factory in Lier.

These Z-shaped beams served to realize 2 spans on the spot. Once mounted, 37 u-caissons were put side by side per 2 layer, on the bottom tooth of the Z-shapes. Pouring a compression layer on these u-caissons resulted in a free mould of 9.4 m and 13.7 m wide. The construction height is however restricted to approx. 1.05 m in the middle of the 2 bridges (the level difference between the bottom of the element – upper side of the compression layer).

Not only the weight was exceptional, 240 tons a beam, but these Z-beams had to be produced in dark grey with e concrete quality C80/95. Some small adjustments had to be made at the Ergon factory, but we succeeded once again to bring this project to a favourable conclusion.

Meanwhile Ergon looks forward to the next challenge!

Technical data:
For this project, Ergon supplied:

KW15 – Preflex beams;

  • 11 preflex beams for the construction of 1 bridge
  • Height 1.1 m, width 0.75 m, length: 42 m, weight 95 tons
  • Prestressed reinforcement: 72 T15-strands
  • Preflection strength 2 x 72.5 tons on the preflexed steel beams (height 1 m, width 0.6 m, thickness of the flanges: 100 mm, thickness of the body: 30 mm)

KW10 – Z-beams and U-caissons:

  • 4 Z-shaped beams and 74 u-caissons for the construction of the 2 bridges


  • Height 2.85 m, width 1 m, length: 43 m, weight 240 tons a piece
  • Prestressed reinforcement: 65 T15-strands
  • Posttensioning: up to 4 posttensioning pipes with each 37 T16-strands per Z-beam

U-caissons long 37 pieces:

  • Height between 0.92 m and 0.64 m, width 0.83 m, length: 15.5 m, weight up to 14 tons a piece
  • Prestressed reinforcement: up to 23 T15-strands

U-caissons short 37 pieces:

  • Height between 0.92 m and 0.47 m, width 0.735 m, length: 11 m, weight up to 10 tons a piece
  • Prestressed reinforcement: 14 T15-strands