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box-girder bridge cells connection arrangement

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For box-girder with depth more than 1/6 of bridge width. one cell will be enough. but for bridges with depth less than 1/6 of bridge width. one cell is not enough. two cells is a better choice. there is no need to have a large number of cells for a bridge with a shallower depth. two cells will be enough. because the increasing number of cells will not enhance transverse load distribution. multiple cells can be connected by the top flange only as shown in figure 1. connecting box-girder cells using top flange only will cause a concentration of stress at the top flange(connection location). the top flange will be overstressed heavily at transverse direction because it will not be able to distribute flexural properly through the cross-section.





Figure-1

the second arrangement is connecting cells through top and bottom flange as shown in figure 2. second arrangement is better and it is recommended to be used to connect box girder cells. in this arrangement, the connection area will not be overstressed and flexural will be resisted more efficiently. 
Figure-2





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