Oostertoegang Amsterdam: Replacement of historic railway bridges

ProRail aims to renew and improve the ageing rail infrastructure in the Netherlands. As part of this vision, four steel bridges and one concrete railway bridge on the eastern side of Amsterdam Central Station will be replaced over the next five years. These five bridges, four of which are over a hundred years old, form an important part of the rail network which connects Amsterdam to the rest of the Netherlands. 

From 2024, one railway bridge per year will be replaced, a necessary step due to the age of the current bridges and the need to extend the platforms. Iv is working with Dura Vermeer, Hollandia, Takke Breukelen, Sterk, CRUX and Mammoet on the Oostertoegang Amsterdam (eastern railway approach to Amsterdam Central Station) project. Iv is responsible for the integral design of the five railway bridges on behalf of Dura Vermeer. What is involved in replacing existing railway bridges in such a busy environment?

A new design for the bridges

Four of the bridges will receive new pillars, abutments and foundations. The fifth bridge will retain its existing abutment, adding a unique challenge to the project. Each bridge consists of three spans resting on concrete pillars and abutments. Iv developed the tender design of the steel bridges and supporting structures into the final design. After the final design, Iv was also involved in the manufacture and installation of the steel bridges.

Although the bridge sections are similar, they are not 100% identical. An accurate and efficient design process was required for this. By (partially) automating the structural analyses and optimising modelling and drawing work, Iv completed the design of the bridges with minimal design work and without increasing costs. Automating the structural analyses also made it easy to assess the feasibility of the contractor’s requirements and preferences. Iv has structurally demonstrated that the foundations can support the bridges and that the steel bridges meet all requirements.

In railway projects, strict physical constraints are associated with safe rail passage. A fixed rail height is required due to the connecting track elements and civil engineering works. The resulting platform height is also essential to allow safe boarding and disembarking of passengers. Additionally, there are restrictions due to elements that pass underneath, such as tramways and roads. The design has considered all these aspects to allow for functional use.

What is involved in replacing existing railway bridges?

The historic railway bridge replacement project brings a number of unique challenges. The substructure is crucial, mainly because existing stamped concrete will be used. This old concrete presents unique challenges due to uncertainties in its cohesion and stiffness. These uncertainties were incorporated into the design by factoring in the upper and lower limits of the properties of the stamped concrete (strength and stiffness). The longitudinal force analysis was also an essential part of the design. This analysis ensures safety and serves as a design tool to optimise the support points. This approach reduced the number of pillars required and achieved cost savings while improving the project’s sustainability.

A further specific challenge in this replacement project concerns the fifth bridge, where the existing abutments and foundations will be used. These were initially designed to standards from the early 1990s, which differ from the current Eurocodes. To ensure that these existing components could withstand the new loads, Iv first carried out archival research using old drawings and calculations. These were then modelled to assess whether the existing substructure was strong enough to support the upgraded bridge safely.

Added to this were technical challenges, such as strict adherence to contractual requirements for permitted drilling zones in the existing structure. The possibilities within the requirements were explored with the client to arrive at an optimal design, as there are also significant safety risks and challenges associated with drilling through the old concrete structure.

Scheduling the work was also a challenge. The availability of train slots is often determined two years in advance. This means that the timing of major works, such as the installation of a bridge, is known well in advance, and the schedule must be strictly followed. This became a challenge when the original steel contractor went into bankruptcy. Suddenly, the team were faced with finding a replacement and adapting the design.

Finally, in the busy area of Amsterdam Central Station, various traffic flows have to be considered, such as train traffic, public transport, motorists, cyclists and pedestrians. To minimise disruption, as much work as possible will be carried out over the water, or transportation will occur via the water.

Creative and innovative

One of the key aspects that makes the project of renewing the railway bridges at Amsterdam Central Station unique is how the challenges encourage the team to remain creative and innovative. “The technical challenges are exactly why we do this work; they make us better at what we do and keep us sharp,” says Martijn Roverts, senior structural engineer at Iv.

“What I particularly like about this project is our common working day every Wednesday in Amsterdam. It’s a dynamic day that brings together the implementing parties, the design manager and colleagues from both Iv and Dura Vermeer,” says Martijn. “These days are invaluable. I would definitely recommend this way of working for future projects. It requires intensive cooperation and coordination between the different disciplines.” His words underline the importance of technical expertise and the ability to work together as a team and find solutions.