Fatigue mechanism and parametric analysis of end hangers in hybrid cable-stayed suspension bridges

Hybrid cable-stayed suspension bridges provide an attractive solution for super long spans, yet the fatigue behavior of end hanger under moving loads remains a critical concern. This study investigated the fatigue mechanism of the end hanger in a hybrid cable-stayed suspension bridge through force decomposition, finite element validation, and parametric analysis. An explicit analytical framework was developed to decompose the moving-load-induced force variation of end-hanger into physically meaningful components, and the proposed framework was validated against finite element results, with only a 1.1% difference in the peak positive value of the end-hanger force influence line. The results show that the fatigue behavior of the end hanger is governed by coupled force components, among which the rotation-related component is dominant because of the rotation mismatch between the first cable segment and the interior cable segments. Then the effects of key structural parameters were quantified. The increase of vertical bending stiffness of the girder, main-cable sag and the bonding zone length can improve fatigue performance efficiently. Moreover, the moving-load-induced response of the end hanger is governed by the coupled stiffness of the girder-cable system. The variation of stay-cable axial stiffness apparently influences both the force range and stress range of the end hanger, while the main-cable axial stiffness aggravates the fatigue demand. An increased hanger axial stiffness from an enlargement section reduces the corresponding stress and significantly improves the fatigue life.