page 1 / 6 Günther Dorrer Kvarnholmsförbindelsen Nacka Bridge Indroduction In connection with the development programme for Kvarnholmen, Nacka Municipality constructed a direct link between Kvarnholmen und central Nacka. The new link is in the northwestern part of Nacka Municipality, by the side of Saltsjön and opposite Djurgarden. The project Kvarnholsförbindelsen, Etapp 1 includes the bridge across Svindersviken bay, a tunnel road through Ryssbergen and a connection to Griffelvägen under Varmdöleden. An architectural competition was held in 2009, and the proposal by KHR/Rundquist Arkitekter for a steel bridge of metallic gold appearance with angled legs proved to be the proposal that best matched Nacka Municipality s requirements and expectations. Nacka Municipality has produced tender documents including both proposal drawings and construction documents. During the design work process, Nacka Municipality and its consultants ascertained that the project was highly complex and that dialogue with contractors was required in order to establish the exact design of the project. Nacka Municipality therefore decided that the procurement for the project would follow the new tendering procedure of the Public Procurements Act competitive dialogue. During this phase of the competitive dialogue Bilfinger Construction GmbH, Bilfinger MCE GmbH and the consultant Leonhardt, Andrä und Partner developed an alternative solution for the bridge. The alternative proposal for the bridge over the Svindersviken bay was a 145 m long arch bridge with composite deck. Superstructure Deck and Arch The Nacka Bridge carries 2 lanes of road traffic and a bicycle lane over the Svindersviken bay and is a combination of an arch with composite superstructure (Fig. 1) and a prestressed concrete deck (Fig. 2) in the side span. The alternative solution was considered as the most natural solution to softly fit in to the landscape and with care consideration of the environment. Looking from the top, the bridge deck is gently curved. This fact leads to a remarkable solution in geometry of main arch beams that have dynamic inclination to the centre of curve to compensate actions of
page 2 / 6 the forces like a motorcyclist driving through it. Each arch beam has an own angle of inclination and own radius to optimize forces in structure. Such approach brings it s delicacy and lightness as a result of rational engineering logic and sensuality of design progress. Fig. 1: Arch bridge with composite deck Fig. 2: Side span
page 3 / 6 The deck structure itself consists of a composite type where a light steel structure provides the structural basis for the crossing. A concrete carriageway slab, designed state of the art, gives the bridge its solid function under the consideration of low maintenance efforts. Staying underneath of the bridge (Fig. 3) the area has been sensible evaluated for the most sensitive solution to maximise an unhindered development of that space by the residents. Fig. 3: 3D-rendering of the bridge Foundations and supports have been placed far outside of this area which provides a wide view to the sea and a generous public space (Fig. 4). The bottom view confirms the light structure with a sight to the structural details.
page 4 / 6 Fig. 4: rendering of the bridge The total width of the bridge is 11.7 m, the roadway accounting 8.0 m and the pedestrian and cycle path accounting 3.5 m of the width. The height of the composite and the prestressed superstructure are the same (h = 2.0 m). The concrete slab has a thickness of 30 cm. The bridge will be supplemented with noise barriers. The steel grades of the steel superstructure are S355 M and S460 M in accordance to SS-EN 10025-4. The arch span is 145 m and the pre stressed span is 48 m (Fig. 5). Fig. 5: Longitudinal section The bridge will describe an even curve between the south and north abutments. The curvature of the longitudinal axis in plan view is R= 489 m (Fig. 6).
page 5 / 6 Fig. 6: Plan view Hangers The hangers will consist of high strength round steel rods grade S460NL. The diameters of the hangers are between 115 mm and 170 mm Fabrication, Assembly and Launching The steel structures of the girder as well as the arch were divided in 10 single elements with a length up to 32 m and a weight up to 80 t. The single steel elements will be prefabricated in the workshop of Bilfinger MCE. After complete fabrication and application of the corrosion protection the steel elements will be brought by truck to the preassembly yard behind the northern abutment. The elements will be placed on temporary supports by usage of mobile cranes. After completion of the preassembly works the complete steel structure will be moved into the final position. For this procedure the superstructure will be relocated from the auxiliary supports and lifted by Self-Propelled Modular Transporter (SPMT). The SPMT will move the steel structure from the pre-assembly yard to the end of the cantilever of the pre-stressed concrete bridge. The SPMT will continue onto the river banks and onto the pontoon unit, which is floating the superstructure in the final position. After the steel arch with the steel superstructure is in the final position, connected with the foundation and the pre stressed superstructure in Axis 3.1, the casting of the concrete deck slap can start. The concrete deck plate of the composite superstructure will be casted with a formwork traveler and a stationary formwork.
page 6 / 6 After completion of the project Nacka Municipality has added not only an additional civil engineering structure but also a sight to its cultural heritage in the area of Stockholm. Due to the architectural design a new landmark will be created. Bilfinger MCE GmbH www.mce.bilfinger.com