The Galecopper Bridge: DSI contributes to Strengthening an important Link on the A 12 Motorway
The Project: Lifetime Safety
The Galecopper Bridge, which crosses the Amsterdam-Rhine Channel in Utrecht as part of the Dutch A 12 Motorway, is approx. 40 years old. The structure consists of two parallel steel bridges with main spans of 180m and two side spans of 70m each. The longitudinal girders of the bridge are carried by stay cables that are attached to two pylons in the middle of each bridge deck.
Since the bridge has been exposed to steadily increasing traffic loads, Rijkswaterstaat, the executive arm of the Dutch Ministry of Infrastructure and Environment, decided to strengthen the steel bridge decks with a layer of high strength concrete. Due to the extra weight of the new concrete layer, the main steel structure of the bridge had to be strengthened as well.
Within the scope of the comprehensive repair work, the bearings and tie downs had to be replaced. Simultaneously, the main spans of both bridge structures were lifted in order to create a larger clearance for ship traffic on the Amsterdam-Rhine Channel. The repair work will ensure a safe use of the bridge for the next 30 years.
Reinforcement of the Bridge Structure: A stable Solution
Along the existing bridges, four 327m long steel box girders were installed – two on the outside and two on the inside. For these girders, new foundation blocks were built on piles. Each girder consists of three parts that were transported to the jobsite on pontoons and then lifted and longitudinally joined together.
These new girders were also connected to the existing steel structure. At the abutments, tie down anchors were installed in order to keep the girders on the bearing plates. At the intermediate supports, the new girders were lifted approximately 0.7m using hydraulic jacks. This way, the girders were prestressed and accommodated some of the loads from the existing bridge structure.
The Tie Downs: Flexibility and Performance
The anchors used to keep the new steel girders on the bearings at their ends were tie downs with parallel strands based on the DYNA Grip® System. The existing tie downs (fully locked steel cables) in the mid-girders of the old bridges were replaced by the new Type DYNA Grip® Tie downs. In total, DSI supplied 12 Type DG-P 19 DYNA Grip® Tie Downs with 19 parallel strands and 12 Type DG-P 31 DYNA Grip® Tie Downs with 23 parallel, 0.62" Ø, St 1860 N/mm2 strands. Each strand is galvanized and additionally protected against corrosion by a PE-sheath filled with wax. The fixed anchorages are located at the upper side of the steel girders, and the stressing anchorages with ring nuts are located at the lower end in the concrete foundation blocks. The length of the tie downs that were used for the steel girders ranged between 5 and 7m.
The tie downs were fitted with DYNA Grip® Anchorages due to the flexibility and high fatigue resistance of this system. The tie downs were installed strand by strand and partly stressed using monostrand post-tensioning jacks. The transfer of the final tensioning forces was made using gradient jacks. DSI Netherlands carried out both the installation and the tensioning work.
Efficient Fire Protection: Load Bearing Capacity in Extreme Situations
The existing, fully locked stay cables are essential for the load bearing capacity of the Galecopper Bridge, which is why the owner decided to have them fitted with a fire protection system. All of the existing stay cables were equipped with fire protection up to 20m above the bridge deck. At each pylon, there are two stay cables at the main span and two stay cables at the side span. In total, there are 16 stay cables, each consisting of 6 parallel, fully locked 76mm Ø steel cables. DSI proposed a new type of fire protection consisting of flexible panels filled with silica powder which have superior insulation properties. The stay cables were wrapped with 1.2m long and 7mm thick panels. Afterwards, rectangular, 220 x 300mm protection girders consisting of two stainless steel half shells were installed around the stay cables. The installation of the fire protection was carried out by DSI in close cooperation with Civiele technieken deBoer BV and Janssen Lastechniek.
Success through Know How and Special Systems
The complex and difficult rehabilitation of the Galecopper Bridge had to be carried out within a very tight schedule in order to obstruct shipping and road traffic as little as possible.
DSI is proud to have contributed to the successful realization of this project with expertise and high quality products.