In the coming decades, Rijkswaterstaat faces the challenge of replacing and renovating a large number of Dutch highway bridges built in the 1950’s and 1960’s. These structures must be renewed in a sustainable, cost-efficient manner while minimizing traffic disruption. The objective is to retain the existing substructure and replace only the superstructure of the bridges, which are in need of replacement. This study investigates the competitiveness of weathering steel concrete composite bridges in the Netherlands, for small-span bridges (15–30 m). Hereby the following bridge variants will be considered for determining the competitiveness:

Variant 1: Existing full reinforced concrete superstructure
Variant 2: conventional painted steel–concrete composite superstructure
Variant 3 : weathering steel–concrete composite superstructure

The research is structured into four phases: (1) a literature review on material behavior, corrosion performance, and durability of unpainted weathering steel under Dutch environmental conditions; (2) structural verification using a real bridge case study to assess Eurocode compliance; (3) a sustainability assessment using Life Cycle Assessment (LCA) and Environmental Cost Indicator (MKI) values for life-cycle stages A1–A5; and (4) an economic evaluation of construction, maintenance, and lifecycle costs.
The literature review highlighted that weathering steel offers substantial maintenance and sustainability advantages but faces environmental constraints in the Netherlands due to high humidity (≥76%) and frequent de-icing salt exposure. The standard Dutch vertical clearance of approximately 4.5 m is below the 6.1 m recommended in international guidelines (ASTM and ECCS) to prevent chloride spray contamination. Effective use of weathering steel thus requires sacrificial thicknesses, optimized detailing, and preventive maintenance to ensure long-term durability. Mechanically, weathering steel behaves comparably to conventional painted steel.
Structural verifications confirmed that variant 2 and variant 3 satisfy Eurocode requirements for bending moment, shear force, and deflection, considering different configurations of the superstructure. Accounting for a 1 mm sacrificial thickness in weathering steel reduces bending moment resistance by 3.5–6%, a small but measurable effect.
The sustainability assessment showed that Variant 3 achieved the lowest environmental impact for A1–A5 stages. The use of low-carbon XCarb® steel reduced total MKI by 50–55% compared to conventional NMD steel in Variant 2, and the elimination of paint provided an additional ~9% reduction. Variant 2 performed better than Variant 1, but worse than Variant 3, while Variant 1 (full concrete) had the highest MKI.
Life-cycle cost analysis indicated up to 30% savings over 100 years for Variant 3 compared to variant 2, mainly due to reduced maintenance and minimized traffic disruptions. Structural mass comparisons showed that Variants 2 and 3 are 53–56% lighter than Variant 1, reducing loads on existing abutments and facilitating replacement while preserving substructures.
Overall, weathering steel–concrete composite bridges are technically feasible, sustainable advantageous, and economically competitive for small-span superstructure replacement in the Netherlands. These findings support the potential of integrating weathering steel into Rijkswaterstaat’s sustainable bridge renewal strategy, offering a robust pathway toward low-maintenance, low-impact, and long-lasting infrastructure.

To describe the behaviour of beams which are loaded on a torsional force it is possible to make use of the Saint-Venant formula, if the beam is unconstrained on both sides. This theory can be used regardless the cross-sectional dimensions of the beam. If the beam is only constrained at one side and unconstrained at the other side, it is possible to make use of the Vlasov torsion theory to describe the behaviour of the beam, however this theory is proven only for open crosssection. In this report it is attempted to prove the Vlaslov torsion theory for rectangular solid cross-sections and for rectangular closed tube cross-section.
It is important to describe a proper method to validate the Vlasov torsion theory. The beam will be constrained only at one side and a torsional external moment will work at the free end of the beam. During the whole validity process it has been chosen to keep the material properties and the external moment the same in order to compare the results. The length of the beams are kept variable to see what the influence is of the length of the beam on the accuracy of the Vlasov torsion theory. First, the maximum horizontal displacement and the maximum normal stress has been calculated by use of the Vlasov equations. Second, the maximum horizontal displacement and the maximum normal stress have been calculated by use of the FEM software Abaqus. These outcomes have been compared with each other by use of a ratio check, namely if the maximum error is within 15 percent it can be stated that the theory is valid for the tested beam length.
From the obtained results it can be stated that the Vlasov torsion theory seems to be valid regarding the maximum horizontal displacement for the rectangular solid cross-sections and the rectangular closed tube cross-sections. The obtained results for the maximum normal stress exceed the maximum allowable error of 15 percent. Regarding the obtained results for the maximum normal stress, the Vlasov torsion theory can not be declared valid for the mentioned cross-sections.