Cable-stayed Bridge Connected to a Chained Floating bridge : A Case Study

Abstract: In Norway there are plans of a ferry-free European road E39 with crossings of eight deep and wide fjords. A newly developed bridge concept that could be used for some of these fjord-crossings is a chained floating bridge. One of the challenges for the chained floating bridge is to create a convenient shipping-lane under the bridge, where one suggestion is to connect the chained floating bridge with a single pylon cable-stayed bridge. The aim of this thesis is to design and evaluate a cable-stayed bridge in connection with a chained floating bridge. The purpose is to evaluate the feasibility of such a design by conducting a case study of the crossing of Bjørnefjorden. A design of a bridge is created for the case based on a literature study of conventional cable-stayed bridges. The bridge design is modelled, analyzed and the structural integrity is evaluated with SOFiSTiK (a finite element software for structural design) according to Eurocode. The study concludes that the concept is feasible for Bjørnefjorden by providing a possible design of a cables-stayed bridge connected to a chained floating bridge with conventional cross sections. The analysis in the thesis confirms the structural integrity of the consept. The bridge design’s main span is 300m long, it has a 25m wide steel box girder where the cables (φ140mm) are placed in two planes with a spacing of 15m along the girder. It has a 184 m high A-shaped pylon with a concrete box section from the foundation up to the girder level (+50m), to the top is a steel box (3.5x3.5m). The bridge is designed with material properties according to Eurocode, where steel class S355 and concrete C45 are used. A parametric research also verifies the design’s feasibility for other geometries of chained floating bridges - where the horizontal reactions on the cable-stayed bridge vary in a range of 107MN-242MN. The parametric research confirms that both the utilization of the cross section and the stability increases with the horizontal reaction from the chained floating bridge. The parametric study also concludes that a width of 8m between the pylon legs decreases the effect on the lower part of the pylon and the support reaction at the pylon when compared with a 12m and a 18m width. However, the average utilization of the girder, cable and steel part of the pylon increases when the 8m width is compared with a 12m or a 18m wide pylon. A fan or radial cable arrangement compared to harp design is more efficient for the cables and the displacements of the girder in Z-direction. They are however, less efficient for the bottom part of the pylon than the harp arrangement.