main girders. The main girders of this bridge are formed of welded hollow steel sections compared to the I sections at the other three bridges described in this paper. The reasons for that were manifold. Since the main and cross girders are fully welded together and no bolted splices had to be foreseen the box girders could be welded air-tight so that no additional internal corrosion protection was required. The outer surface area of a box is typically smaller than that of an equivalent I section and there are no dirt accumulations on the bottom flange possible. Such advantages regarding maintenance made this solution the preferred one of the Belgian road authorities. Last but not least the elevation from below is more fair compared to open sections and it matched architectonically better to the outline design provided by the client: a single box girder with a central cable plane. In the side span the main girders turn into post tensioned concrete upstands.
Fig. 9: Deck cross section of K03 over Albert Canal
The same design that has been developed for the Ting Kau bridge has been used for the joints between the precast panels and the steel girders. Thanks to the comparatively wide top flange of the main girders, which corresponds to the width of in-situ concrete joint (see Fig. 9), it was possible that the reinforcement of the cantilevering precast panels could be anchored in this joint to support the almost 3 m wide service path, without extending the cross girders beyond the main girders. This way a very slim and elegant edge with about 30 cm height was created and the image of a box girder with wings was emphasized. A large portion of the steel grid, consisting out of main and cross girders, with a size of about 70 m by 30 m could be prefabricated in the workshop and transported to site with large barges. After completion of the concrete side span, the masts and abutments, the steel grid was lifted to temporary towers that rested directly at the quay walls during a remarkably short closure period of the channel. Once connected with the remaining steelwork at the mast and the opposite abutment, the cables with a spacing of 12 m and the skewed precast panels with a typical size of 9 m by 4
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Number 2 June 2016
m and thickness of 25 cm have been installed step by step beginning from the mast. The cantilever panels have been supported by temporary steel girders (Fig. 10).
Fig. 10: Installation of the precast panels(Š Jan De Nul Group)
Not only a composite deck for the main span was used, also the masts are made out of a steel cross section that was partially filled with concrete. To achieve a very slender mast which still allows interior access, high strength steel was used to carry down the main compression loads. The composite cross section was mainly used to restrain the steel plates from local buckling, so that the full yielding capacity could be used without additional stiffeners and in order to increase the robustness in case of cable failure. 3.4 Signature Bridge Delhi The "Signature Bridge" as the new landmark of New Delhi connects the city Ghaziabad and its surrounding across the river Yamuna to the inner city. The dynamically shaped pylon consists of 2 inclined legs, which are rigidly connected to the deck girders and bend mid-way. The upper portion of the pylon anchors the back-stay cables as well as the main-span cables, arranged in a harp like manner. The tip of the pylon is created by a 30 m high steel-glass structure, which can be illuminated to create a landmark visible from afar at night [4].
Fig. 11: Virtual image of Ornamental Painting on the Pylon
The Bridge and Structural Engineer