Multi-objective green design model for prestressed concrete slabs in long-span buildings

Prestressed concrete (PC) slab using tendons is one of the most frequently used slab systems in the construction of buildings with long-span slabs. To simultaneously minimize the construction cost and the environmental impact, a green design model for PC slabs in long-span structures is necessary. In this paper, a multi-objective green design model for prestressed concrete slabs (MGDPCS) was developed to minimize both CO₂ emissions and the construction costs of PC slabs. MGDPCS provides the optimized PC slab thickness, diameter and yield strength of the rebar, size and yield strength of the tendon using the Non-dominated Sorting Genetic Algorithm (NSGA-II) for the input PC slab size and load. Furthermore, the effects of changes in the long- and short-side of span and tendons of PC slabs on construction costs and environmental impact are analyzed using the proposed model. Accordingly, we developed two indicators, that is, the environmental and economic scores and the eco-friendly coefficient, to evaluate the performance of the practical green designs using MGDPCS. To verify the applicability of MGDPCS, the model was applied used to analyze the designs of PC slabs in an actual six-story industrial building with a slab span of 10 m × 10 m. The results showed that the optimal designs obtained from MGDPCS outperformed existing slab designs for buildings by 8.12% and 13.62% based on the reductions in CO₂ emissions and costs, respectively.