New stay cable bridge crosses the river Ijssel
The "EILANDBRUG" stay cable bridge crosses the IJssel river in a new section of the N50 motorway near the city of Kampen. The total length of the bridge is 381 m, the pylon is 93.5 m high and the main span is 150 m long and 20 m wide.
This bridge, designed by the Bouwdienst Rijkswaterstaat, was built for the Province Overijssel.
Hollandia B.V., the main contractor of the bridge, built the steel structure of the main span and the bascule bridge. The subcontractor was a joint venture of Hegeman Nijverdal B.V. and Strukton Betonbouw B.V., responsible for the civil part of the project.
DSI Netherlands was awarded a contract to supply and install the post-tensioning in the concrete approach bridges and the stay cables for the main span.
The construction of the foundation for the pylon started in August 2000 and the bridge was completed in December 2002.
Approach Bridges and Bascule Bridge
The north and south concrete approaches are 91 and 130 m long, respectively. Thanks to a combination of high strength concrete class B65 that incorporated Ø 0.9 m weight reducing tubes, and the 13 strand longitudinal DYWIDAG Post- Tensioning Tendons, it was possible to achieve very light and slender sections with a total thickness of only 1.25 m.
The approach bridges were erected between August 2001 and March 2002.
DSI Netherlands delivered and installed the weight reducing tubes and the post-tensioning (approx. 171 t strands Ø 15.7 mm).
The pylon legs and the main transverse girder at the deck level were built using class B65 high strength concrete with massive cross sections. Starting from the deck level at 21 m, special climbing scaffolding was used for erection complete sections of pylon legs. The pylon was erected prior to the main span and it was necessary to use temporary supports for the inclined pylon legs at the level of 58 m.
At the top a transverse wall joins the legs of the pylon. The stay cable anchorages are located here. The lower anchorages of the back stays are located at the deck of the ballast caisson at the north end of the bridge. During the erection of the main span the ballast in the caisson had to be increased proportionally in order to keep the pylon in balance.
The main span of the bridge is designed as a composite steel-concrete structure. The deck was erected incrementally by using 14.5 m long and 20.0 m wide prefabricated bridge sections.
The basic steel frame consists of two longitudinal main girders joined by four transverse girders. The anchorages of stay cables are located in the main girders. Four prefabricated concrete slabs 13.7 x 3.2 m placed on the steel frame and connected by means of cast in place concrete joints, form the bridge deck.
The main span was erected between April and August 2002. The excellent cooperation between all parties involved made it possible to achieve a very fast erection cycle of seven days with the major steps as follows:
installing a new steel section with the aid of a floating crane and a temporary fixing frame,
securing the new section to the old one by welding joints at the main girders,
removing temporary securing frame, installation of stay cables and the 1st stressing phase,
placing concrete prefabricated slabs with the aid of a floating crane,
re-stressing the stay cables, casting concrete joints,
repeating the cycle for next section.
During the erection of the main span the back stay cables were installed and stressed. After installing and stressing of the first pair of back stay cables the temporary support of pylon legs were removed.
The 3rd stressing was carried out on all stay cables after the last section of the main span was completed and the final 4th stressing phase was completed after the asphalt overlay was placed on the deck.
DYNA Grip® Stay Cables
The main span is suspended on 2 x 9 = 18 stay cables. The shortest stay cables are about 68 m long and consist of 28 strands; the longest are approximately 165 m in length and consist of 46 strands. The back stay cables (2 x 3 = 6) are approx. 106 m long and consist of 86 strands each.
DYNA Grip® Cables with anchorages type C37, C55 and C91 were used in this structure.
Approximately 187 t of Ø 15.7 mm grade FeP1860 (ultimate load 279 kN ) galvanized, wax filled and individually PE-coated strand was used. An outer HDPE-sheathing provides additional protection for the parallel bundle of strands of each stay cable. The HDPE-tubes are incorporate an external helix in order to reduce the risk of wind and rain induced vibrations.
The HDPE-tubes are fixed at the pylon and at the deck there is a sliding joint to allow changes in the length due to temperature variations. Steel anti-vandalism tubes up to 4.5 m above the deck level also protect the stay cables.
The strands pass through recess tubes at the deck side and the pylon side and are fixed by wedges in the anchor blocks. Because deviators are installed at the end of recess tubes strands are compressed to a compact bundle in the free length. Above the deck special clamps were installed on the stays in order to make it possible to install optional external hydraulic dampers if extensive vibrations were to occur during the service life of the bridge.
DYNA Grip® Anchorages are designed and tested to withstand 2 million fatigue cycles with an upper load of 0.45 of the ultimate static cable load and an amplitude of 200 MPa.
Installation of Stay Cables
Recess tubes and anchor blocks were installed during prefabrication of the main span steel sections and after erection of the concrete pylon. For each pair of stay cables, HDPE-tubes with connecting parts at the ends were welded on the deck. Furthermore, strands were cut to the required length and individual PE-sheathing was partly removed in order to be able to anchor the individual strands by wedges in the anchorages.
After a new steel section of the main span was welded to the previous section, the real installation of stay cables began. The HDPE-tubes were lifted by a crane and fixed at the pylon. Due to stressing the first strands in the HDPE-tubes they were “stretched” between both anchorages. Subsequent strands were pulled through the HDPE-tubes from the deck into the pylon anchorage and then into the deck anchorage and fixed with wedges. They were individually stressed using the DYWIDAG ConTen-Method. In this method two monojacks are used. The first strand is tensioned to the required calculated force. A “reference jack” is placed on the first strand and the subsequent strands are tensioned one by one with the aid of a “working jack”. The working jack is hydraulically coupled to the reference jack and automatically stops tensioning when the force in both jacks becomes equal. Due to deformations of the pylon and the deck the stressing force in subsequent strands decreases gradually. After tensioning the last strand of the bundle the required stay cable force is obtained with equal stresses in all individual strands.
The stressing forces are based upon the global calculations of the stay cable forces and bridge deformations during erection and a “DSI-translation” of these data into Stressing Records is prepared for the ConTen-Method. All stressing phases were carried out with the ConTen-Method.
After the final stressing deviators and damper clamps were installed, antivandalism tubes were placed and caps filled with wax were installed to protect the anchorages.
Thanks to thorough planning and effective coordination between all parties involved in design and execution of the bridge the “EILANDBRUG” was completed on schedule.
The city of Kampen received a beautiful new landmark that also helps the community solve its local traffic problems.