Abstract: With increasing emphasis on environmental sustainability in the construction industry, carbon emissions in the design of large-scale foundation pit strut systems has become a critical issue that must be taken into account. While traditional designs prioritize cost-effectiveness, they often lack consideration of environmental performance. This paper proposes a building information modeling (BIM)-based enhanced constraint method and integrates it into the NSGA-Ⅱ framework to achieve multi-objective optimization of foundation pit strut design. First, carbon emission calculation criteria for foundation pit support systems are established, and the boundary conditions are defined, covering life-cycle stages including material production, transportation, construction, demolition, and recycling. On this basis, an enhanced constraint method is proposed to transform design codes into quantitative constraint conditions and combine them with the NSGA-Ⅱ algorithm. Structural information is extracted through a BIM platform to improve the accuracy and practicality of the optimization process. Finally, two typical foundation pit support cases are analyzed to verify the effectiveness and applicability of the proposed method. Compared with traditional designs, the optimization algorithm demonstrates significant improvements in both cost efficiency and carbon emission reduction. Specifically, cost optimization efficiency and carbon performance improve by 40.9% and 30.1%, and by 25.3% and 20.9%, respectively, in the two cases. This approach provides a more scientific and effective optimization methodology for foundation pit strut structural design.

Key words: NSGA-Ⅱ, enhanced constraint, foundation pit strut, multi-objective optimization, building information modeling (BIM)