Reinforcement of Neckerstraat bridge

The bridge on Neckerstraat over the A7 in Purmerend is a concrete bridge whose decks are supported by intermediate supports with nib structures. These intermediate supports are known as table structures. Because Rijkswaterstaat (RWS) had concerns about the structural safety of these table structures, Iv was commissioned to carry out recalculations and provide an analysis of the condition of the bridge and the strengthening measures required.

Iv carried out an extensive recalculation and concluded that the hanger reinforcement and tension ties in the table structures did not meet current safety requirements. Based on these findings, RWS asked Iv to design the strengthening measures for the Neckerstraat bridge to make it safe and suitable again for all traffic, including heavy traffic. This was an urgent project: the bridge strengthening had to be carried out at a rapid pace.

The intermediate supports consist of wide table structures with nib details. In the past, these nib structures were not always adequately reinforced, which was also the case for the Neckerstraat bridge. Iv therefore carried out a recalculation at both a preliminary and a refined level. This calculation concluded that the nibs themselves still complied, but that the hanger reinforcement and tension ties in the table structures required strengthening. This called for a complex technical solution that would allow traffic flow to be maintained during the works. Iv developed the strengthening design in close collaboration with RWS, with weekly coordination on the technical aspects and scope of the solution.

A smart strengthening design prevented the need to replace the bridge in full. Iv designed a solution in which the hanger reinforcement of the nib was strengthened using anchors installed transversely through the table structure. The table structure was also overlaid, with additional longitudinal reinforcement installed. In total, around 50,000 holes were drilled to install the additional reinforcement and anchors. This was a complex challenge, as it was critical not to strike the existing reinforcement in the pier table.

The selected strengthening method allowed traffic to continue using the bridge throughout the construction works. Although traffic ran on narrowed lanes, the number of lanes remained the same, keeping disruption to a minimum. Another advantage was that the works were relatively straightforward to carry out. The methods and materials used were proven and widely available. Construction consortium Savera successfully completed the works in 2024.