Research on the Impact of Long-Term Down Deflection from the Long-Span Concrete Girder Bridge on the Structure Stress

This thesis wages a study on the characteristic of long-term down deflection deriving from the large-span concrete continuous girder bridge, introducing the equivalent bending moment instead of mid-span deflection, both of which can produce an effect on the structure stress, building the relational expression between equivalent bending moment and mid-span deflection with equal stiffness principle and mechanics of materials axiom employed, and hereby gaining the calculation expression of the stress increment triggered by the deflection. Basing on a pre-stressed concrete continuous girder bridge with it´s span combination of 70m+110m+70m and a pre-stressed concrete continuous rigid-frame bridge with it´s span combination of 75m+130m+75m, this thesis calculates the stress increment triggered by mid-span deflection, with the results showing that the mid-span deflection has a bigger influence on the structure stress. When the deflect value is bigger, beam will crack and there exists a close connection between deflection and crack.