Parametric analysis of carbon dioxide emissions associated with RC beams made with lightweight concrete under different design scenarios
These are the results from two parametric analyses involving reinforced lightweight concrete beams. Beams are continuous with two spans of equal length. The first set corresponds to downstand beams and the second set corresponds to flat beams (or wide-shallow beams). Over 3.25 million design scenarios are considered, obtaining the reduction in total load upon the supports, the flexural/longitudinal reinforcing steel consumption, the cement consumption and the equivalent carbon dioxide emissions associated with steel and cement consumption. For the estimation of the tons of CO2 associated to each ton of steel, the following report was considered: https://www.worldsteel.org/en/dam/jcr:1b7492b1-15f5-401a-88f1-7ae488e0553f/SteelTalks%2520May%252020%20717%2021_Asa%2520Ekdahl.pdf For the estimation of the tons of CO2 associated to each ton of cement, the following report was considered: https://docs.wbcsd.org/2009/06/CementIndustryEnergyAndCO2Performance.pdf For the mix design of lightweight concrete, the method by Bogas and Gomes was considered (doi:10.1617/s11527-013-0029-1). This dataset is associated to the paper "A parametric study to assess lightweight aggregate concrete for 2 future sustainable construction of reinforced concrete beams" by Vives, I., Varona, F.B., Tenza-Abril, A.J. and Pereiro-Barceló, J. published in the Special Issue "Complex System Modeling Methods Applied to Sustainable Development", in Sustainability, 2021 (in press, DOI pending).
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The two parametric analyses used the following design variables: • Live load: 2, 3, 4 and 5 kN/m2. • The tributary width TW of the floor slab supported by the beam: six possible values ranging from 3.5 m to 6 m, at 0.5 m intervals. • Cross-sectional dimensions. Two different typologies have been considered: (i) downstand beams, with depths between 35 and 55 cm (at 5 cm intervals) and widths of 25, 30 or 35 cm; and (ii) flat beams or wide-shallow beams (WSBs) with a depth equal to that of the floor slab (27 cm) and seven different values of the cross-sectional width, from 40 to 70 cm at 5 cm intervals. • Concrete cover (to longitudinal rebar center): 3.5 cm to 5 cm, at 0.5 cm intervals. • Concrete compressive strength: 20, 25, 30 and 35 MPa. • Density class: three types of LWC with classes 1.6, 1.8, 2.0 plus normal weight concrete. • Cement type: 42.5 or 52.5 MPa. • Span length: ranging from 4 m to 7 m, at 0.5 m intervals. • Redistribution factor: from 1 to 0.7, at 0.05 intervals. This parameter corresponds to the linear analysis with limited moment redistribution carried out to design the flexural/longitudinal reinforcements of the beams at the critical sections in ULS. The beam-and-block system has a constant depth of 27 cm. The precast-prestressed concrete beam and the infill blocks have a weight of 0.27 kN/m and 1 kN/m, respectively, with a repetition interval of 70 cm. The area of in situ concrete (conventional or lightweight) is 0.0467 m2/m (for a repetition interval of 70 cm). The dead load is 2 kN/m2 and the yield strength of steel is 500 MPa. Eurocode 2-1-1 is used for ULS and SLS verifications. The outcomes of these analyses are the following: • Maximum ULS design load (in kN) transmitted to the three supports of the continuous beam. • Cement consumption (in kg) of the cast ‘in situ’ LWC concrete used in both the beam and the tributary floor slab that is supported by it. • Mass of steel (in kg) used in the longitudinal reinforcements of the beam. • Estimation of the equivalent carbon dioxide (CO2) emissions associated with the cement consumption and steel used as longitudinal reinforcements. • Compliance of the designs with the Serviceability Limit State (SLS). The cracked cross-sectional inertia of the critical sections is calculated to obtain the tensile stress of the longitudinal reinforcement under the relevant SLS combination of loads. This stress is then used to verify cracking without direct calculation and the limiting ratio of span length L to effective depth d, to omit an explicit analysis of the vertical deflection.