Abstract: To alleviate the contradiction among the relatively high carbon emission levels, emission reduction costs and schedule during the railway bridge construction phase, a carbon-constrained multi-objective optimization (CCMO) model was proposed. The carbon footprint characteristics of each stage were analyzed quantitively by establishing the carbon emission calculation model for the railway bridge construction phase. Using material consumption, number of equipment shifts, and energy consumption as decision variables, a multi-objective optimization model encompassing carbon emissions, costs and duration was established. The Pareto frontier solution set was solved by the MOEA/D algorithm, and the optimal solution was selected by integrating the TOPSIS method based on subjective preference weights. Key parameters were identified through sensitivity analysis, and a case study of a mountainous railway bridge was taken for validation. The research results indicate that: ① The carbon emissions during the material production stage account for 79.01%, with steel and concrete contributing 64.30% and 25.50%, respectively. In the construction stage, direct emissions from mechanical equipment account for 63.57%, while the cumulative emissions from the superstructure, foundation, and substructure account for 96% of total emissions. ② By adjusting the material and energy consumption coefficients to 0.89 and 0.90 respectively, and increasing the equipment shift coefficient to 1.06, the optimal scheme can achieve a 19.3% reduction in carbon emissions, while also maintaining reasonable control over costs and construction duration. ③ Sensitivity analysis indicates that material consumption is the key control parameter, with a ±10% variation potentially causing an approximate fluctuation of ±8% in carbon emissions.

Key words: bridge engineering; railway bridge; carbon emissions; multi-objective collaborative optimization; MOEA/D algorithm

摘要： 为缓解铁路桥梁建设阶段较高的碳排放水平与减排成本、工期之间的矛盾，提出了一种基于碳排放约束的多目标协同优化模型(CCMO)。通过构建铁路桥梁建设阶段的碳排放计算模型，对各环节的碳足迹特征进行量化分析；以材料用量、设备台班数和能源消耗量为决策变量，建立碳排放-成本-工期的多目标优化模型；采用MOEA/D算法对Pareto前沿解集进行求解，结合基于主观偏好权重的TOPSIS法选取最优方案，通过敏感性分析识别关键参数，并以某山区铁路桥梁作为实例进行验证。研究结果表明：① 材料生产阶段碳排放占整体建设阶段的79.01%，其中钢材、混凝土分别贡献64.30%、 25.50%；施工建造阶段中机械设备直接碳排放占该阶段排放的63.57%，而上部构造、 基础工程与下部构造累计占总排放的96%； ② 最优方案通过将材料、 能源消耗系数调至0.89、 0.90，设备台班系数升至1.06，可实现碳排放降低19.3%的目标，成本与工期亦得到合理控制； ③ 敏感性分析显示材料用量为核心调控参数，±10%变动可引起碳排放约±8%波动。

关键词: 桥梁工程； 铁路桥梁； 碳排放； 多目标协同优化； MOEA/D算法