Stress Analysis Of PC Box Girder Under Three-Directional Prestresses

For the advantages of box-beam, prestressed concrete box-girder bridges have bean applied widely in the passed twenty years. There are quite a lot cracks appearing in the constructions and services, especially on the webs, therefore, three dimensional analysis becomes necessary. Base on a discussion on the characters of box-girder, the stress of box-girder is analyzed when three-directional prestressing force is acted. In order to obtain a detailed information of stress of webs when the vertical prestressing force is applied, a three-dimensional finite element model is created with the commercial code ABAQUS. For different values of vertical prestressing force, the stress of webs is calculated and analyzed. The results signify that the vertical prestressing is significant for reducing the principal tensile stress, but while the vertical prestressing reaches a certain value, the principal tensile stress will change slowly. The stress of webs is also calculated when the temperature field is applied. The results signify that the stresses of the ribs and webs are influenced greatly when the temperature load is present. Additionally, the shear-lag effect on the mechanical behavior of box beam is analyzed and discussed in this paper. The longitudinal stresses of the top and the bottom of the box-girder are calculated and analyzed when the prestressing force is applied.