ABSTRACT
In order to investigate the possible structural diseases brought to the deck of the existing prestressed concrete box girder bridge, the stress state of the existing box girder before and after widening were analyzed using finite element method in this paper. The possible structural diseases and their mechanisms that were brought to the upper plate and flange plate of the existing box girder were studied. The main parameters considered include the shrinkage and creep effect of the new concrete bridge, the uneven settlement difference between the old and the new box girder, the temperature gradient and the vehicle live load on the whole widened box bridge. Results showed that the inner flange of the old box girder were generally in the state of large tensile stress, the main reason for which was the shrinkage and creep effect difference and the uneven settlement difference of the new and old bridge. And the tensile stress was larger than tensile strength of C50 concrete, which would most likely cause crack in the deck plate of box girder. Hence, reinforcement measures are needed to be designed carefully. Meanwhile, the transverse deformation of structure had exceeded the distance between the anti-seismic block and the web of box girder at the end cross section, which would most likely squeeze anti-seismic block. Therefore, it is necessary to limit the length of continuous bridge that needs a widening work.
