*Article* **Research on Optimal Arch Rib Inclination of Large Span Highway CFST through Arch Bridge**

**Zengwu Liu 1,2, Yuexing Wu 3, Chengwei Wang 2,4, Yonghui Fan 2, Chao Luo 2,\* and Shaorui Wang <sup>2</sup>**


**Abstract:** To investigate the reasonable range of the inclination angle of arch ribs, a spatial finite element method was employed based on a concrete-filled steel tube (CFST) basket-handle through an arch bridge with a span of 360 m. A spatial finite element model was established using Midas/Civil software, which was verified with actual bridge data. The effects of different arch rib inclination angles were investigated under static loads. The structural natural frequencies, linear elastic stability coefficients, internal forces, and displacements were comprehensively considered to determine the reasonable range of the inclination angle. The results show that when the inclination angle ranges between 8◦ and 10◦, the first, third, and sixth natural frequencies of the structure are increased. It effectively improves the lateral and torsional stiffness of the arch ribs while ensuring optimal out-of-plane stability of the arch ribs. Compared with the parallel arch, the stability is improved by 20.2%. The effects of angle variation on displacement and internal force of the arch ribs were not significant. Considering all indicators, the optimal range of the inclination angle for the arch ribs of 300-m-level highway CFST arch bridges is suggested to be 8~10◦.

**Keywords:** steel tube concrete truss arch; highway basket-handle arch bridge; arch rib inclination angle; finite element method; lateral stability
