Post-Tensioning Systems and Stay Cables for Ewijk Cable Stayed Bridge
The Waal Bridge near Ewijk in the Netherlands is part of the A50 motorway, one of the country’s most important north to south corridors. The existing bridge with a main span of 270m was built between 1971 and 1976 and is one of the longest bridge structures in the Netherlands. Due to the importance of the A50, the Rijkswaterstaat, the executive arm of the Dutch Ministry of Infrastructure and the Environment, decided to widen the A50 motorway between Ewijk and Valburg in both directions from two to four lanes each over a distance of 7km.
For this purpose, a second bridge running west of the existing bridge was built over the Waal River. In addition, the motorway junctions of Ewijk and Valburg were expanded.
The entire project was carried out within the scope of a Design-Build contract. The consortium responsible for its execution and design is Waalkoppel, a consortium consisting of Mobilis, Van Gelder B.V. and DYWIDAG Bau GmbH. The architectural design of the new Waal Bridge is adapted to the appearance of the existing steel bridge so that the two bridges will form a unified architectural entity in the future. However, a post-tensioned concrete structure with additional stay cables was chosen for the new bridge.
The bridge is a typical post-tensioning bridge with a total length of 1,055m. The bridge construction is divided into the southern approach area with spans of 75.0m + 90m + 90m + 90m + 105m = 450m, a main span of 270m as well as the northern approach area with spans of 105m + 85m + 75m + 70m = 335m. The extraordinary bridge design by the German engineers Kinkel und Partner included a maximum construction depth of 4.25m for the post-tensioned concrete superstructure, with the superstructure depth in the large span across the river being reduced to 3.35m. Two small hollow box girders were laterally connected using approx. 21.80m long precast girders, which results in a total bridge width of 32.5m. Bonded PT strand tendons are located in the hollow box girders and between the lateral girders.
The Waal Bridge was built using a combination of incremental launching and cantilever construction. Starting from the abutments, both approach bridges were simultaneously constructed using the incremental launching method. The incremental launching area extends approximately 20m into the main span area. After completion of the incremental launching section, the launching noses were removed in the southern and northern sections.
DSI supplied a total of 1,200t of strand tendons for the longitudinal and transverse post-tensioning of the bridge deck. Simultaneously, the two parallel, 52m high pylons and the form travellers were built. Thanks to the combination of these construction methods, negative impact on the valuable landscape of Waal River was kept to a minimum. The concentric post-tensioning during incremental launching was carried out using prefabricated PT tendons.
The Type SUSPA Systems Prefabricated Tendons were installed into the reinforcing cage of the floor and roadway slabs within a short time span.
This procedure significantly reduced interference with the other subsections (in particular with concrete formwork and reinforcement).
In the final state, eccentric and parabolic DYWIDAG PT Tendons were used in the longitudinal girders of the hollow boxes to complement the concentric post-tensioning that had been installed while construction was in progress. For these tendons, the strands with a maximum length of approx.108m were pushed into ducts that had been previously positioned.
In the transverse direction, the two hollow box girders were connected to each other using precast concrete elements. Prefabricated tendons with 8 and 9 strands respectively were also used between the U shaped precast elements. The tendons were anchored at the interior girders of the two hollow box girders using SD Plate Anchorages.
In the main span, the bridge’s bearing capacity is augmented by 19 strand DYWIDAG Tendons that are located externally in the hollow box girders. A staggered arrangement without deviation was chosen for the tendons. The external tendons were anchored at the girders using brackets.
The 270m long main span was erected using the stayed cantilever method in sections of approx. 5m. To stabilize the cantilever sections, temporary stays were installed in addition to the permanent DYNA Grip® Stay Cables. Afterwards, the temporary stays consisting of the 15 and 19-0.62" DYWIDAG Strand Post-Tensioning System with MA Anchorages were successively removed in accordance with the construction progress.
Both stay levels of the cable stayed bridge are fitted with two different types of stay cables. DSI produced and supplied 40 DYNA Grip® Stay Cables each of types DG-P 73 and DG-P 91 in lengths of 57m to 126m totaling 850t for this project. The stay cables were arranged in pairs.
DSI also provided the equipment necessary for installation and carried out the complete installation of the stay cables. The strands were installed into the PE sheathing using pushing equipment with driving rollers. The pushing equipment, which was set up at the tip of the pylon, pushed down a steel wire inside the PE sheathing towards the superstructure.
There, the steel wire was connected to the strand, and subsequently, the pushing equipment pulled the wire with the attached strand upwards through the pylon anchorage where the strand was anchored.
Additionally, the 32 longest stay cables were fitted with external dampers to limit cable vibrations. The dampers were installed following the completion of work at the DYNA Grip® Stay Cables.