Sustainable Design of Reinforced Concrete Structures through CO2 Emission Optimization

Abstract

Efforts are being made to achieve more efficient operation of buildings, with the goal of reducing the construction industry's contribution to energy consumption and greenhouse gas emissions. That contribution also includes the energy embodied in structures; that is, the energy consumed in the processes of extracting, manufacturing, transporting, and installing construction materials (including recycled materials) and elements. In particular, in spite of the use of additives such as fly ash, reinforced concrete (RC) structures, which are large consumers of cement, are responsible for a sizable proportion of worldwide carbon emissions. These emissions can be reduced significantly through the more efficient use of both concrete and steel that can be achieved by optimization. Modern optimization tools are now available that make it possible to perform large volumes of calculations efficiently that are applicable to a wide variety of structural engineering problems. This study presents an optimization approach developed with a view to allowing decision makers to balance sustainability and economic objectives. To illustrate this approach, an RC frame under gravity and lateral loads is considered in this paper. It was found that, depending upon the parameter values used in the calculations, the design optimized with respect to the CO 2 footprint yields a CO 2 footprint that is lower (by 5% to 10%) than the design optimized with respect to cost. The reduction can be smaller for low-rise structures and other structures with predominantly tension-controlled members. However, for structures whose members predominantly experience large compressive forces, such as high-rise buildings, the reduction may be more significant. This also may be true of certain prestressed and poststressed concrete members. Additional research aimed at ascertaining the extent to which this is the case is warranted.

Analysis of CO2 Emission Characteristics of Concrete Used at Construction Sites

“…Yeo et al [12] proposed an optimization approach developed with a view to allowing decisionmakers to balance sustainability and economic objectives considering an RC frame under gravity and lateral loads. Gartner [13] analyzed the practicality of replacing Ordinary Portland cements with alternative hydraulic cements that could result in lower CO2 emission per unit volume of concrete.…”

Contribution to sustainable seismic design of reinforced concrete members through embodied CO2 emissions optimization

“…Typical concrete -typical steel impact (R=0.38); high concretelow steel impact (R=0.13) and low concrete -high steel impact (R=1.25). Furthermore, to consider the fact that values of reinforcement steel CO2 emissions even smaller than the low limit given in [23] have been reported in literature [9,25] a scenario with high concrete CO2 impact and zero reinforcing steel CO2 footprint (R=0) is also examined herein. The latest scenario is used to envelope all scenarios with R<0.13.…”

“…They found that designs for minimum CO2 emissions produce 1% less CO2 footprints and they are 1% more expensive than minimum cost-based designs. Furthermore, studies [7][8][9] comparing optimum designs of RC frames for minimum CO2 footprint and construction cost report that the former lead to 4-15% less CO2 emissions than then latter. They also conclude that the actual reductions depend on the cost and environmental impact ratios of reinforcing steel to concrete materials [9].…”

Cost and CO2 emission optimization of precast–prestressed concrete U-beam road bridges by a hybrid glowworm swarm algorithm

“…Park et al [19] suggested an optimization technique for steel reinforced concrete columns in high-rise buildings that simultaneously considers the structural cost and CO 2 emissions at the structural design phase. Yeo and Potra [20] carried out a similar study for RC moment frames, while Medeiros and Kripka [21] proposed the minimization of monetary and environmental costs of rectangular RC column sections. The work of Fernandez-Ceniceros et al [22] presents a decision criterion based on the embodied CO 2 and the overall cost of one-way floor slabs.…”