Abstract:Diagonal cracks in the webs of cantilever-constructed box-girder bridges are widespread, posing a direct threat to the safe use of bridge structures. However, the existing single-factor analysis methods are difficult to comprehensively explain the causes of their formation. To study this problem in depth, an integrated model simultaneously considering the prestressing system, load superposition effect, and environmental and material factors is established. This model is used to conduct the multi-factor coupled analysis, and able to calculate the coupled influence values of three key factors, such as radial forces from bending tendons, stress field redistribution due to the Poisson effect in anchorage zones, and thermal stress. Based on the statistical analysis of typical engineering cases, two critical time control parameters are proposed that are the window period for vertical prestressed tensioning and the minimum age required for longitudinal tensioning. In addition, a temperature-load-age coupled control matrix is established. Findings demonstrate that in the coupled interaction, the weightings assigned to radial force, thermal effects and construction sequencing are 45%, 30% and 25%, respectively, providing a solid theoretical support for crack prevention. By implementing a series of design optimizations and construction improvements including controlling the angle threshold of downward-bending bundles, managing temperature during layered concrete pouring, and optimizing the design of external prestressing reinforced nodes, the crack resistance of the structure can be significantly enhanced.
