Probabilistic life-cycle environmental impact of conventional and emerging steel frames in seismic zones

This paper presents a comprehensive framework for life-cycle carbon emission assessment of steel frame structures in seismic zones, with a particular focus on emerging self-centering steel structures with reduced residual deformation and enhanced seismic resilience. The proposed framework is illustrated through a life-cycle embodied carbon (EC) emission study on an office building located at Los Angeles, USA. Different structural bracing systems are considered for comparison, namely, conventional concentrically braced frame (CBF), bucking-restrained braced frame (BRBF), and self-centering braced frames (SCBFs). The life cycle assessment (LCA) of EC emissions mainly involves four phases: (1) components manufacturing phase, (2) construction phase, (3) operation and maintenance phase, and (4) EC emissions related to seismic hazard. For the last stage, the engineering demand parameter (EDP) is obtained through incremental dynamic analysis (IDA), and combined with the fragility function and the seismic risk curve to obtain the expected EC emissions related to seismic hazard over the life cycle. Among other findings, the results show that: (1) In the manufacturing process, the EC emissions of the emerging SCBFs are slightly increased (by up to 1.4%) compared with the two other conventional steel frames. (2) During the construction, operation, and maintenance phases, there is no difference in the EC emissions for the different structural systems. (3) The EC emissions related to potential seismic risk are reduced by up to 65.3% when the proposed self-centering structural system (P-SCBF) is used. (4) Compared with the CBF, the total EC emission over a 100-year lifespan can be reduced by up to 14.6% when the P-SCBF is used. Due to the limited deformation capacity of braces, the EC emissions of CBF and BRBF are more sensitive to increases in the intensity measure (IM). Since a building becomes difficult to repair when the maximum residual inter-story drift exceeds 0.5%, BRBF and CBF are more susceptible to demolition due to unacceptable residual deformation, leading to higher EC emissions. The EC reduction efficiency of the emerging steel frames become more remarkable with increasing life span.