DYWIDAG Products for Bridge with Unique Design: De Oversteek, Nijmegen
In Nijmegen, one of the oldest cities in the Netherlands, a new bridge crossing the Waal River was opened for traffic in November 2013. The 1,400m long bridge is known as “De Oversteek” and consists of different sections that were built using different construction techniques. The main span is a 285m long steel arch bridge. The approach bridges on both sides of the main span are built as a combination of conventional concrete and lightweight foam concrete. Post-tensioned concrete viaducts are positioned at both ends of the approach bridges and are connected to the local road network.
Most of the arch spans are 42.5m long and 25m wide. The approach bridge at the north side of the river consists of 15 arches, and the south side consists of 5 arches. BAMInfraconsult proposed a unique concrete design for the arches: Each arch consists of a conventional concrete shell structure with a curved bottom plate and vertical side walls. These concrete shell structures were then filled with lightweight foam concrete, providing a flat deck for traffic. The bottom part of the concrete arches is only 0.5m thick in the middle and is supported by approx. 1.1m thick V-shaped transverse concrete girders. The transverse girders rest on two concrete columns rising from a concrete foundation block on piles.
DSI supplied, installed, stressed and grouted the DYWIDAG Post-Tensioning Strand Tendons for all transverse girders. As a rule, 5 Type 27-0.62", 1860N/mm² DYWIDAG Strand Tendons were used per transverse girder. In each construction cycle, the columns and V-girders were built prior to the construction of the concrete arches. Three forms were used for each arch. Furthermore, DSI supplied Ø 63.5mm GEWI® Bars that were installed at the highest points of the concrete arch shells. The bar tendons ensure the stability of the arches during erection - particularly after the removal of scaffolding and formwork.
In a few locations, temporary diagonal DYWIDAG Strand Tendons were placed between the top of the columns and the next foundation blocks. Two tendons with 31 PE-sheathed strands per column were applied for additional safety against progressive collapse. DSI also supplied, installed and tensioned these strand tendons and de-tensioned them once all arches had been completed.
The bridge deck of the main span consists of two longitudinal steel girders and an orthotropic steel deck with a 150mm thick concrete top layer. The 60m high and 285m long steel arch structure is the longest arch bridge in Europe. Fully locked steel stay cables connect the arch structure and the bridge deck.
Construction work on the main span was carried out in a site yard next to the river. The assembly of the arch structure using temporary supports in an area similar to a dry dock allowed the transportation of the complete steel arch on pontoons from the site yard to its final position on the main concrete pillars at both sides of the river Waal. The spectacular floating in place of the arch structure was successfully completed in April 2013.
The dynamic behavior of the stay cables will be monitored for one year. DSI supplied frictional dampers for some of the stay cables in order to investigate the differences between damped and undamped cables.
The two viaducts were designed with variable lengths and widths in order to provide suitable connections to the existing local roads. Both viaducts are built as pre-stressed concrete structures. 42 Type 27-0.62", St 1860N/mm² DYWIDAG Strand Tendons were used for the Oosterhoudsedijk viaduct. 46 Type 22-0.62", St 1860N/mm² DYWIDAG Strand Tendons were used for the Weurtseweg viaduct. The length of the DYWIDAG Tendons that were supplied, installed and grouted by DSI varied from 32 to 50m.
The co-operation between the various parties involved in the design and construction of this very challenging project was pleasant and successful.