Abstract：Research purposes: For controlling the appearance of web inclined crack in large span box Girder Bridge, the paper researched on two influence factor of web's principle stress, which involved the construction form of vertical prestressed reinforcement and web thickness change in different fashion.
Research methods: Research method: Using bridge analysis software, the paper calculated web principle tensile stress in different change fashion of web thickness. At the same time, aiming at disadvantage of general vertical prestressed reinforcement, other two layout imagination of vertical prestressed tendon was put forward in paper. Space finite element method was adopted to analysis web principle stress comparing each conformation form of vertical prestressed reinforcement by using Ansys software.
Research results: The paper deduced principle stress curves in different change fashion of web thickness; principle stress change curve in different construction form of vertical prestressed reinforcement; and node’s first principle stress contour of local beam segment.
Research conclusions: (1) the adoption of web thickness change fashion was thought an important influence factor in crack control, and transitional change fashion should be used to the full. (2) comparing the general vertical tendon, the advantage of U type vertical tendon represent to bring monolithic precompression stress on web concrete in the U region, which restrict the appearance and magnitude of web principle tensile stress. The influence analysis for new conformation form of vertical prestressed tendon offered referenced opinion for continuous system box girder in reasonable arrangement of vertical.
2006, Vol. 23 
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