Efforts are being made to achieve more efficient operation of buildings with a view to reducing the construction industrys 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 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 efficiently large volumes of calculations 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 we considered a reinforced concrete frame under gravity and lateral loads. It was found that, depending upon the parameter values used in the calculations, the CO2 footprint is lower by about 5% to 15% if the objective function on which the optimization of the design is based is the carbon footprint than if the objective function is the cost. The reduction can be smaller for low-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 may also be true of certain prestressed or poststressed concrete members. Additional research aimed at ascertaining the extent to which this is the case is warranted.
Citation: Journal of Structural Engineering-ASCE
Pub Type: Journals
Carbon emissions, cost optimization, CO2 footprint optimization, greenhouse gas emissions, reinforced concrete, optimization