Analysis Of Box Girder Space Effect For An Extradosed Cable-stayed Bridge

Extradosed cable-stayed bridge, with such characteristics as short tower, rigid beam, concentrated cables and beautiful shape, has been rapidly developed and wide-ly used both at home and abroad in recent years. From the point of structural charac-teristics, extradosed cable-stayed bridge is a transition between cable-stayed bridge and continuous beam bridge. Stay cables only bear a small part of load while the beam’s bending and shearing resistance bear a considerable amount of load. Most of the extradosed cable-stayed bridges in the municipal construction are over 30 meters wide. The stress of the wide beam is complex and the spatial stress is quite uneven. Zero block of the main beam, for example, has got not only a complex structure, but also quite variable imposed load, so it is difficult to grasp the uneven stress. In addi-tion, the current specification is mainly applied to soft and slender beam concrete structure. However, for the increasing number of wide box girder structures, obvious-ly, the current specification has its own limitations. As a result, once cracks happen to the concrete, it’s difficult to find the corresponding checking stress from the design checking method in the current specification. According to these situations, this thesis, taking an extradosed cable-stayed bridge over Yinghe as the engineering background, first uses Midas/Civil 2012 to build a space truss finite element model of the whole bridge and makes a detailed analysis of the overall mechanical characteristics. Next, the thesis uses Midas/Fea 3.6 to build the space finite element model of zero block and analyzes the stress distribution characteristics at the stages of the largest cantile-ver and the completion of the bridge. In a further step, the thesis builds the spatial en-tity models of 6 to 8 blocks and uses integrated checking stress theory to make a re-fined analysis of the crack resistance of 7 block. The research of this thesis can pro-vide some references for the design and construction of extradosed cable-stayed bridges.