Structural assessment and multi-year maintenance plan Zeeland Bridge

The challenge

The Zeeland Bridge spans over five kilometres across the Oosterschelde. At the time of its opening in 1965, it was the longest bridge in Europe. In 2015, the bridge was designated a national monument due to its significant architectural value. The bridge consists of 54 piers with 52 spans in between and a movable bascule bridge, all functioning as one system. After decades of exposure to wind, salt water, traffic and ageing, the bridge has become a vulnerable structure. Its unique configuration makes long-term behaviour and the remaining service life difficult to predict. As the structure approaches the end of its service life and damages continue to develop, current maintenance measures are failing to prevent further deterioration. Although the Province of Zeeland has built up maintenance knowledge, it remains uncertain which measures will remain effective in the long term. The challenge lies in shifting from reactive to strategic maintenance.

A masterpiece of engineering

Prefabrication played a key role in the design of the Zeeland Bridge. The concrete structure consists of a sequence of 52 prestressed T shaped elements, each with a deck length of 95 metres. Each T element consists of interconnected bridge segments, an A frame pier structure and a caisson on top of three foundation piles, all connected by prestressing. Each T element, excluding the piles, has a total weight of approximately 2,790 tonnes.

The foundation piles are constructed from 6 metre long prestressed segments and vary in length from 25 to 50 metres. The differences in the length of the foundation piles depend on the water depth, the bearing capacity of the soil, and the type of connection between the T elements. The scale is of its foundation is enormous: more than 60% of the bridge remains permanently underwater. Only 40% of the bridge is visible, of which less than 1% consists of the bascule bridge.

From a technical perspective, each of the 54 piers functions as an individual bridge. The T elements are connected midway between the piers by means of shear keys and shock absorbers. These connections ensure that the elements remain aligned under heavy traffic, while still allowing expansion and contraction. The exact behaviour of these flexible connections was designed manually, and their long-term effect on the prestressed structure remains unknown. It is expected that the flexibility of the T elements decreases over time due to deterioration of the prestressing steel and ongoing concrete hardening, resulting in high forces in the bridge connections. This increases the risk of failure of a bridge section.

In addition, prefabrication, limited concrete cover and the saline environment have led to continuous deterioration of the structure. This increases the risk of corrosion of the prestressing reinforcement. For years, concrete coatings have been applied in an attempt to limit the problem, concealing the signs of damage.

Key characteristics

EUR 250 million (nowadays)
Building time: 1962-1965
National monument since 2015
Length total: 5,022 metres
54 piers: 52 spans x 95 metres
315,000 tonnes of concrete
7,400 tonnes of reinforcing steel
3,300 tonnes of prestressing steel
7,000 metres of foundation piles

Our activities

The Province of Zeeland awarded Walhout to develop a long-term maintenance strategy for the Zeeland Bridge. The project started with a review of the complete maintenance archive, followed by extensive inspections and field investigations of the concrete structures. Walhout carried out advanced structural analyses, dynamic traffic load studies, finite element modelling and deformation predictions, to gain deeper insight into the bridge’s behaviour, force distribution, strength and lifespan. The complete bridge structure was assessed for structural safety.

A summary of our engineering activities:

Background study of maintenance records
Inspection of all 54 concrete pier structures
Field investigation of concrete works
Underwater inspection of concrete piers
Analysis of dynamic traffic loads
FEA analysis of all concrete piers
Prediction of behaviour of T elements
Structural assessment (NEN 8702)

The findings formed the basis for a multi-year maintenance strategy and roadmap for 2022-2037. The technical assessments indicate that, after nearly 60 years in operation, the bridge has a limited remaining service life. Several critical vulnerabilities have been identified. Based on these findings, multiple strategic pathways were outlined, ranging from continued maintenance and revitalisation to partial reconstruction or full replacement. In the short term, the focus is on extending the service life of the bridge, while in the longer term, replacement or alternative solutions such as a tunnel are being considered.

The expected investment could amount to several billion euros. The impact on Zeeland is substantial. Walhout’s study marked an starting point for the Province to engage with the Government of the Netherlands, to explore potential alternatives and the opportunities for funding and collaboration. In 2026, the national government announced that it supports the province in its search for a new transport connection through the Multi-Year Programme for Infrastructure, Spatial Planning and Transport (MIRT). A first step forward.

A summary of our consulting activities: