Nemetschek Engineering User Contest 2009 • Category 3: CAE Civil Works 109 3 The mobile bridge has one span of 56 m consisting of 2 opening parts of 28 m allowing for the passage of large ships. When closed the hydraulic jack functions as a suspension cable. A pair of masts is situated at the hinging point of the mobile section. Each of these masts is connected to the mobile section through a fixedlength stay and to the fixed bridge section by a variable length 0.56 m diameter piston stay. The fixed-length stay forms a non deformable triangle with the mast and the mobile section. The mast is used as a lever to tilt the bridge open or closed. The piston stay powers the opening and closing mechanism and forms a deformable triangle with the mast and the static section. In order to keep the piston force as small as possible (for operating and maintenance costs), a first large top counter weight is placed running between the mobile mast heads and a second smaller bottom counterweight under the bridge deck. Temse bridge will be opened to the public in 2009. This piston stayed bascule bridge with its slender elements does not dominate but complements the existing monumental 1950’s truss girder bridge. The engineering ingenuity of the design lies in total integration of the kinematics into its structure. Because of the elegantly detailed finishes, the atypical moulds for the abutments and the subtle lighting scheme, the bridge will blend into its environment and contrast with its neighbour. At Ney and Partners’, we have been using Scia Engineer for global as well as local models. The steel box girders were designed according to the Eurocode 3 for steel structure on basis of the internal forces computed in the Scia Engineer model. The model consists of linear 2D beam elements. We have used numerical elements with a connecting node each 4 meters approximately. As the geometrical characteristics vary with the thickness of the plate, we would have to define manually more than 100 elements and their cross-section. Therefore we used the XML functionality to automatically create the cross-section, the nodes and the 2D elements in Scia Engineer. The traffic loads, of which the position moves along the bridge, were also created using the XML functionality. It allowed a quick link between a list in MS Excel and Scia Engineer. The internal forces (Nsd, Vsd, Msd) as well as the deflection were computed with Scia Engineer and used for the final design calculations. As the bridge is not symmetriccally by nature, two models were needed; this could have been time-consuming without the automatic creation via XML. Other models were used for other necessary calculations such as: assessment of the 3D behaviour of the mobile bridge, assessment of the 3D behaviour of the static span, design of the concrete slab, and other detailed calculations of specific parts of the structure. “Tweede Scheldebrug” - Second bridge over the river Scheldt
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