Rhine Bridge Hard - Fussach Part 3 - The superstructure

Due to the high damage potential in case of a possible flood , the discharge capacity of the Rhine is to be expanded from 3,100 m³/s to a maximum flow rate of 4,300 m3/s (HQ300). The 255 m long Rhine bridge between Hard and Fußach must therefore be adapted to ensure the primary framework conditions for flood protection. In addition, the standard cross-section of the supporting structure no longer meets today's traffic engineering requirements. The new Rhine bridge Hard - Fussach, which is planned as a 4-span steel composite bridge with a dissolved cable structure, has three new piers, of which two of the pylons support the cable structure. The structure (4-span girder) has span lengths of 50 m, 125 m, 50 m and 31,6 m. This results in a total span of 255.60 m. The stiffening of the structure above the main span supports is in the form of a harp-shaped span. Due to the low height of the four masts and the resulting shallow inclination of the cables, this is a resolved cable structure that helps to optimize the overall stiffness in the area of the river piers. The architecturally designed steel masts, which consist of a rectangular steel box cross-section, have a height of approx 12m. Construction phase: Superstructure: The construction of the concrete carriageway slab begins at the beginning of October 2021. For this purpose, a 100-ton composite formwork carriage, a mobile formwork unit with a length of 25 m, will be pre-assembled and lifted into individual parts of up to 15 tons at the end of October. The first concreting of the carriageway slab will start at the beginning of December 2021. The final concreting of the carriageway slab will take place at the beginning of April 2022. In mid-April 2022, pylons with a unit weight of 60 tons will be transported to the construction site and then lifted into place and assembled using a heavy truck-mounted crane. The architecturally designed steel pylons, which have a height of 12 m, together with the 20 stay cables of the span form the visual centerpiece of the structure. Immediately afterwards, the installation of the cables is started. Each rope package consists of 7-strand high-tensile stay cables, which are bundled into a rope package of up to 99 strands. The time-consuming tensioning process follows a complex tensioning sequence in which strand is installed strand by strand. All strands are prestressed simultaneously in several tensioning stages at both anchorage points on the underside of the bridge. A total prestressing force of up to 900 tons will be applied to each rope package. Between May and July 2022, 120 tons of steel strands with a total strand length of 100 km will be installed. The fixed point of the entire bridge is located at the western abutment. This makes it possible to design this abutment as a rigid frame corner and, in particular, to transfer longitudinal forces and uplift forces monolithically from the superstructure to the substructure. Due to the edge field stiffened by the span, bearings and roadway transitions can be dispensed with here. The abutment on the other side, on the other hand, absorbs all longitudinal strains of the bridge with a total expansion distance of up to 36cm. Due to the choice of bridge design, the number of deck crossings was reduced to 1. Subsequently, the construction of the edge beams is started. A formwork carriage is used for this purpose. After assembly of the mobile formwork construction, which will be suspended from the cantilevered carriageway slab, construction of the up to 8m wide edge beams will begin as early as mid-August 2022. The edge beams will be produced section by section in a total of 28 concreting sections. After that, the gray top coat, a 2-component high-solid polyurethane top coat with micaceous iron oxide, will be applied by spraying. After completion of the concreting work on the edge beams, the prefabricated bridge railing and guard rails will be installed. Following the installation of the asphalt layers, the bridge can be opened to traffic in November 2022, just over two years after the start of construction.