Optimization of Arch Rib Inclination on Arch Bridges (Case Study: Kali Kuto Bridge)

Optimizing the geometric parameters of arch bridges is essential for achieving material efficiency and indirectly minimizing negative environmental impacts. This study quantitatively evaluates the effect of arch rib inclination on structural performance to determine the optimal design configuration in accordance with SNI 1729:2020. A parametric Finite Element Method was utilized to analyze seven bridge models with arch rib inclinations of 0°, 5°, 10°, 15°, 20°, 25°, and 30°. The evaluation focused on internal forces, steel capacity ratio, deflection, structural weight, and structural performance. The analysis results indicate that an arch rib inclination of 20° is the optimal configuration, achieving the highest structural performance index of 0.987. At this optimum angle, the structural weight is reduced by 5.9%, and the deflection reaches a minimum of 63.3 mm, indicating superior vertical and lateral stiffness. Mechanically, this geometric modification activates a spatial frame mechanism that efficiently redistributes flexural demands into axial forces. Consequently, the combined internal forces on the cross beam arches remain highly efficient, utilizing a maximum of only 11.8% of their nominal capacity. It also minimizes the tensile force on the hangers, thereby lowering localized working stress and providing a larger safety reserve. Ultimately, this study validates that proper geometric optimization can significantly improve material efficiency, which indirectly aligns with the Sustainable Development Goals (SDGs) by minimizing the overall environmental footprint.