Optimization of the ring-segment division scheme for the arch ribs outsourcing concrete in rigid skeleton reinforced arch bridges

This study presents the first comprehensive multi-objective optimization framework for rigid-skeleton reinforced (RSR) arch bridge construction, addressing critical gaps in existing empirical and single-objective approaches. We develop an integrated methodology that combines NSGA-II optimization with a novel Structural Stability Index (SSI) for quantitative Pareto solution selection, validated through systematic testing across seven construction configurations. Using the Tian'e Longtan Bridge as a case study, both 1:10-scale model experiment and finite element analysis were conducted to validate the proposed approach. The optimization method employs working platform lengths as design variables, constrained by segment dimensions. Sensitivity analysis identified optimal NSGA-II parameters: a crossover probability of 0.92 and a mutation probability of 0.02, which achieved superior convergence and solution diversity. Across seven construction configurations (2-4 rings, 6-10 working platforms, 5-7 segments), the method consistently improved structural performance, achieving maximum reductions of 8.56% in compressive stress, 57.41% in tensile stress, and 22.56% in crown deformation. The Structural Stability Index was developed for Pareto solution selection identified the three-ring, eight-working-platform, five-segment scheme as optimal (index value: 5.9196). Validation through moving-load experiments and influence-line superposition confirmed result accuracy, with a maximum relative error of 4.08%. These findings provide valuable references for optimizing construction schemes for similar arch bridges projects.