LCA-Based Investigation of Environmental Impacts for Novel Double-Beam Floor System Subjected to High Gravity Loads

Abstract

In populated downtown areas, a floor system with secured environmental performance is needed to reduce greenhouse gases (GHGs) and global warming problems related to buildings. This study aims to assess environmental impacts on a novel double-beam floor system subjected to high gravity loads. Life cycle assessment (LCA) was conducted to investigate the environmental impacts on the reduction in construction materials by calculating global warming potential (GWP) in the structural design phase. For different structural systems, the environmental performance was compared based on the GWP, and the contributions of structural elements to the GWP in each structural system were analyzed. The rotational constraints induced by the beam-end concrete panel can significantly reduce the GWP of the double-beam floor system by up to 13.8% compared to the conventional beam-girder system. Thus, the double-beam floor system reinforced with the concrete panel can be a candidate for eco-friendly structural systems in underground structures requiring high gravity loads. This result provides valuable findings that the structural effect on the rotational constraint of the concrete panel was quantitatively evaluated by converting it into an environmental impact.

Development of Optimal Design Method for Steel Double-Beam Floor System Considering Rotational Constraints

“…In addition, the bolted connections between the double-beam and the main girder were used to increase in situ constructability. However, since the bolted connections hardly generated a negative moment at the ends of the double-beam, the effect of reduction on the material quantity by applying the DBX system was not significant under the high gravity loads where the live load exceeded 6 kN/m 2 [19]. In the DBO system, a positive moment in the center of the double-beam was decreased, as a negative moment was induced at the ends of the double-beam due to the rotational constraints from the concrete panel.…”

“…In the steel double-beam floor system with the concrete panel, the material quantity of structural members is determined by the weight of steel and concrete. While there is some contribution of the concrete panel to the total material quantity, the environmental contribution of the concrete panel based on GWP is very low, about 10% of the total [19]. In addition, when a quantity-optimized cross-section of the double-beam is determined, the thickness of the concrete panel related to the material quantity of concrete is calculated from Equation (6).…”

“…The dead load was 5.2 kN/m 2 including the slab thickness and the floor finishing. The live load was divided into five categories considering the usage of the underground space in the downtown area: 2.5, 4.0, 6.0, 8.0, and 12.0 kN/m 2 (see previous work [19] for detailed information about the live loads). The dimensions of the structural plan for the steel double-beam floor systems were summarized in Figure 2, and MIDAS-Gen [32], a commercial structure analysis program, was used for frame analysis.…”

“…where CO 2, Embodied represents the embodied CO 2 emission of whole building materials (see detailed calculation process in [19]) and CF is the characterization factor for the GWP (1.00 kgCO 2 -eq/kg from IPCC 2013 [33]).…”

“…To improve the constructability of the beam-column connection in the steel-concrete composite floor system, we proposed a steel double-beam floor system in previous works [7,19] as shown in Figure 1. The steel double-beam floor system is a composite floor system composed of steel-reinforced concrete (SRC) columns, steel beams, and concrete panels.…”