Design and Construction of New Shah Amanat Bridge in Bengal

The main bridge of the New Shah Amanat Bridge is a continuous prestressed box girder extradosed bridge with span arrangement of(115+3×200+115) m.The main girder adopts the type of single cell box girder with thin walls and with diagonal struts installed inside the box.The stay cables,arranged in single cable plane,are threaded through the pylons via the deviation saddle tubes installed in the upper pylon columns,the two ends of the stay cables are anchored to the connection point of the top plate of the main girder and the diagonal strut.The pylon is composed of pedestal,lower pylon column and upper pylon column.The sections No.0 and No.1 of the box girder of the superstructure were all cast in-situ on the scaffoldings and temporarily fixed to the pier top to form T frames.The remaining sections of the main girder were constructed by balanced cantilever cast,using the triangular form traveler,and the closure section was erected by lifting frames.The cast-in-situ sections of the box girder in the side spans were cast on scaffoldings.The pylon was cast step by step using set-shaped steel formwork.In order to facilitate the installation of the form traveler for box girder casting,the construction of the stay cables was carried out one section lagging behind the box girder construction.The structural characteristics of the bridge enable the engineering economy of extradosed bridge to play to the utmost.