Rock anchor hanger effect on single-tower earth-anchored suspension bridge mechanical performance: An analytical model and multi-objective golden eagle optimization

The application of a composite saddle in single-tower earth-anchored suspension bridges (STEASBs) replaces the tower on the steep slope side, which is a cost-effective solution that improves bridge safety and provides environmental protection for the steep bank slope of the valley. However, this novel bridge design needs an appropriate model to evaluate the effect of rock anchor hangers on the structure in the non-girder area and adjust their parameters to optimize the mechanical response of the whole bridge structure. This study proposes an approach to quickly evaluate the most unfavorable load cases of the STEASB and further optimizes the structural parameters of rock anchor hangers to enhance structural safety. An analytical model for the STEASBs under the live load is proposed and verified by the finite element model (FEM), with the maximum relative error not exceeding 7.37%. Combined with the golden eagle optimizer (GEO), the most unfavorable load cases of the corresponding design indices are yielded. The Pareto optimal solutions for the spacing, cross-sectional area, and initial tension of the vertical rock anchor hangers are obtained through multi-objective optimization to improve the mechanical behavior of STEASBs. In addition, it is clarified that the main function of rock anchor hangers is to reduce the peak value of the stress amplitude of the hangers and girder-end rotation, providing a theoretical basis for the STEASB design.