Built at the end of the 19th century, the Marly-Le-Roi viaduct needed to be renovated in order to adapt the structure to the density of rail traffic on this very busy line. With a length of 283 meters, the aging bridge deck, made of puddled iron, had to be replaced in its entirety.

Given the particularly dense urban environment and the small footprint, the transverse shifting technique was chosen from among the proposed variants. This solution was indeed the best adapted to the configuration of the construction site and had multiple advantages: limited impact on railway operations, reduction of traffic disruption to a minimum for users, faster and less costly.

  • Owner and client
    SNCF Réseau
  • Delivery date
  • Partners on this project
    VINCI Construction France / Baudin Chateauneuf / Soletanche Bachy France / ETF /MTS

Key figures of this deck replacement project

The viaduct consisted of a steel deck with 5 spans, supported by 4 piers and 2 abutments at its ends. The new deck adopts a mixed steel/concrete structure, of the double-girder type. The existing bearings have been kept but reinforced.

  • 2,000t
    Weight of existing deck to be unloaded
  • 4,000t
    Weight of the new mixed deck to slided
  • 500t
    Load capacity of the crane used to remove the old deck sections
Marly le Roi viaduct in France Steel deck replacement

Slid out the old deck and slid in the new composite steel and concrete deck

This operation, which is considered the most complex part of the project, consists of sliding first the old deck and then the new one sideways using a system of hydraulic jacks. Built in 1883, the bridge is located on Line L of the Transilien rail network in a very built-up area near Marly-le-Roi station, and carries nearly 150 trains each day.

The project was carried out in five phases over a two-and-a-half-year period, limiting the disruption to rail traffic to a few weekends in 2017 and then seven consecutive weeks in the summer of 2018 to complete the work.

Sliding operation biggest challenge

The biggest difficulty of this steel deck replacement operation was the design and the realization of the connection between the existing structure and the backbone put in place to allow the deck to be slided.

Temporary piers of more than 20 m in height were built to support the new deck during its construction, and then to carry out the operations of lsliding the new deck and removing the old one. The structures rested on displacement saddles specially designed by Freyssinet for this project.

Marly le Roi viaduct in France Steel deck replacement
Marly le Roi viaduct in France

During these operations, the displacements of the piers were monitored to ensure that the sliding and pushing forces did not cause deformations exceeding the calculations.

Strand jacks and Air Pad slidings were supplied by our sister company, Hebetec Engineering. The control of the jacks was carried out for each operation from a centralized control station, ensuring optimal and meticulous synchronization.

Once the old deck had been pushed to a temporary pier, 11m long sections were cut by flame cutting and then removed using a 500T crane. On the ground, these sections were then broken up into smaller pieces using an excavator equipped with a hydraulic shear and then removed from the site.