Study on the spatial mechanical behavior of the cable tower anchorage zone in long-span curved T-shaped rigid-frame extradosed bridge for high-speed railway

This study investigates the spatial mechanical behavior of the cable tower anchorage zone in a long-span curved T-shaped extradosed cable-stayed bridge under operational loads, based on the case of the Changtu River Bridge on the Chongqing-Qianjiang high-speed railway. Through detailed finite element modeling, the stress distribution and load-transfer mechanism within the "raindrop-shaped" strand-guiding saddle anchorage are analyzed. Key findings reveal a parabolic distribution of vertical stress in both the high-strength grout and the concrete below the saddle, with significant load concentration in the curved arc segment. Vertical tensile stresses generated above the saddle may adversely affect the bonding interface. Transverse splitting stresses exhibit distinct "M-shaped" and "W-shaped" patterns at depths of 0.8-1.2 m and 0-0.8 m, respectively. Parametric analysis indicates that the principal tensile stress in the grout decreases with larger saddle arc radius r but increases linearly with the cable force increment ratio λ. Conversely, the vertical compressive stress in the concrete beneath the saddle is inversely related to r and directly proportional to λ. An optimal saddle arc radius between 5 and 5.5 m is proposed to mitigate stress concentrations and improve mechanical performance. These results provide valuable insights for the design and construction of anchorage systems in extradosed cable-stayed bridges subjected to complex spatial load conditions.