随着国家对绿色低碳发展需求的不断深化，建筑业作为我国碳排放主要领域之一，是实现“双碳”目标的重要攻坚方向，因此亟需加快建立和完善基础设施全生命周期碳排放评估体系。作为混凝土结构中的重要组成部分，预应力分项因具有良好的耐久性和抗裂性且节省材料等优点，近年来在工程中受到广泛应用。然而，目前业界对预应力分项工程的碳排放研究有限，尚未形成系统完善的评估体系和计算方法。为此，本文开展预应力分项工程全生命周期碳排放研究，旨在识别预应力分项工程碳排放的主要来源和关键环节，以便于有针对性地制定节能减排措施，助推我国早日实现“双碳”目标。本文主要的工作和成果如下：（1）研究了预应力工程全生命周期碳排放计算方法。通过进行预应力工程的生命周期划分和清单分析，建立了一套相对全面的预应力工程全生命周期碳排放理论模型。基于预应力分项工程的设计、施工特点，提出了一套预应力工程全生命周期碳排放算法，并选用4个工程案例对算法和理论模型进行验证。（2）开展了混凝土结构用预应力钢绞线的碳排放的比较研究。基于建材生产、施工建设、运营维护三个生命周期阶段对有粘结、无粘结、缓粘结预应力进行比较，提出了三种预应力钢绞线碳排放因子的计算公式及建议计算系数，进一步完善了预应力工程的碳排放计算参数。通过对比分析，得出缓粘结预应力钢绞线的碳排放量最低，有粘结预应力钢绞线综合碳排放量最高的结论。（3）开展了预应力混凝土结构与钢筋混凝土结构、钢结构碳排放的比较研究。多方面对比预应力混凝土结构与钢筋混凝土结构、钢结构的结构特点，并基于工程案例对比结构的碳排放量，得到预应力混凝土结构更节碳、更环保的结论。（4）预测了预应力工程未来十年的全生命周期碳排放量。基于预应力钢绞线的主要消费市场，对其产量数据建模分析预测，结合工程案例应用的数据，得出2033年我国预应力分项工程的全生命周期碳排放量预计在3381.86-4510.63万吨区间内，预计占当年全国建筑业碳排放总量的1.3%-1.8%。本文提出并建立了预应力分项工程全生命周期碳排放研究模式和计算模型，并对其进行了理论验证，为预应力分项工程碳排放核算问题提供了一个切实可行的方案，为解决建筑行业碳排放核算问题拓宽了研究思路。
With the growing emphasis on green and low-carbon development in our country, the construction plays a crucial role in achieving the "dual carbon" target, as it is one of the major contributors to carbon emissions in China. Therefore, it is urgent for the construction industry to accelerate the establishment and improvement of a life cycle carbon emission assessment system for infrastructure. As an important component of concrete structure, prestressed subprojects have been widely used in engineering in recent years due to their exceptional durability, crack resistance, light weight, and material saving. However, the industry nowadays lacks comprehensive research on the carbon emissions associated with prestressed subprojects, and a systematic and complete evaluation system with a calculation method is yet to be developed. In light of this, the purpose of this paper is to investigate the life cycle carbon emissions of prestressed subprojects. This research aims to identify the primary sources and critical factors contributing to carbon emissions, and facilitate the targeted development of energy-saving and emission-reduction measures, which will contribute to China‘s timely achievement of the "dual carbon" target. The main work and achievements of this paper are listed as follows: (1)The calculation method for life cycle carbon emission in prestressed subprojects has been studied. Through the life cycle division and inventory analysis of prestressed subprojects, the paper establishes a relatively comprehensive theoretical model for carbon emissions in the life cycle of prestressed subprojects. A carbon emission algorithm for the life cycle of prestressed subproject is proposed, considering the design and construction characteristics of prestressed subprojects. To verify the algorithm and theoretical model, four project cases are selected.(2)This paper conducts a comparative study on the carbon emission of prestressed steel strands used in concrete structures. It compares the carbon emissions of bonded, unbonded, and slow-bonded prestressing methods across three life cycle stages: building materials production, construction, operation & maintenance. This paper proposes calculation formulas of the carbon emission factors for three kinds of prestressed steel strands. Meanwhile the suggested calculation coefficients are provided to further improve the carbon emission calculation parameters of prestressed subprojects. The study also included a comparative analysis of the carbon emission calculation results for the three types of prestressed steel strands, among which the carbon emission of slow bonded-prestressed steel strand is the lowest, and the comprehensive carbon emission of bonded prestressed steel strand is the highest. (3)A comparative study on carbon emissions of prestressed concrete structures, reinforced concrete structures, and steel structures is carried out. The structural characteristics of these structures are compared and analyzed in various aspects, and the carbon emissions of the structures are compared based on project cases. The study concludes that prestressed concrete structures exhibit higher carbon savings and have a more environmentally friendly profile compared to reinforced concrete and steel structures. (4)The life cycle carbon emissions of prestressed projects in the next ten years are predicted. Based on the main consumer markets, this paper establishes a model to analyze and predict the output data of prestressed steel strands. Combing the data of engineering case application, this study predicts that the carbon emissions of prestressed subprojects in China in 2033 will range from 33.81 million to 45.10 million tons, accounting for 1.3%-1.8% of the total carbon emissions of the construction industry in the country in that year.In conclusion, this paper presents a research and calculation model of life cycle carbon emissions of prestressed subprojects. The proposed models are validated theoretically, offering a practical and feasible scheme for carbon emission accounting in prestressed subprojects. This work broadens the research perspective for solving carbon emission accounting issues in the whole construction industry.
