A Quantitative Investigation of the Carbon Savings in Structural Design Based on the Evolution of the Design Codes

Abstract

There have been several iterations of structural building codes over the past decades, with varying structural design methodologies. The unintentional effect that the evolution of the structural design codes had on the carbon dioxide emissions of structural elements was investigated in this research report. As the effects of climate change become more prevalent, such as increased surface temperatures which lead to extreme weather events, understanding the unintentional carbon dioxide reductions in structural design is essential to meeting the greenhouse gas emission goals from the construction sector, such as the Sustainable Development Goals (SDGs) set out by the United Nations. This research investigates the difference in the carbon dioxide emissions, measured in kgCO2-equivalents, that reinforced concrete beams and columns generate when designed using the Code of Practice CP114 (1960s) and the Eurocodes (2010) structural design methodologies. Concrete is a widely used engineered material due to its many advantages, such as strength, versatility, workability, abundant and cheaply accessible primary materials and relatively cheap manufacturing processes. However, cement production emits a significant quantity of carbon dioxide and other greenhouse gases. In the construction sector, a primary method of reducing emissions is by reducing the required quantities of materials. A reduction in the concrete quantity required for an element to perform its intended function can lead to a reduction in the embodied carbon of the element, provided that a large volume of reinforcement is not required to sustain the loads. Embodied carbon is the amount of greenhouse gases emitted during all stages of a product's life, including extraction, transport, manufacture, and installation (EPA, 2023). The global carbon dioxide emissions are continually being monitored by the United Nations and other organisations. This is done to accurately report on, and minimise, carbon dioxide emissions and the subsequent effects of climate change. Hence, it is necessary to investigate and report any carbon dioxide emissions reductions in the construction industry. Two structural design codes were used to evaluate the embodied carbon of two structural elements, namely a simply supported beam and a column in a concrete frame office building, subject to permanent and imposed loading, as stipulated by the structural design codes. These structural design codes were in use more than 50 years apart. In Ireland, the Eurocodes are currently in use, whereas the British Standards Code of Practice CP114 was in use in the 1960s and 1970s. The findings of this research are that across the designs of both elements, there was a decrease in the quantity of concrete and reinforcement required to sustain the design loads in the Eurocodes, which confirms the hypothesis of this research paper. This research project only investigated the effect of reduced material quantities on the embodied carbon of the elements. The effects of partially replacing the cement in the concrete with Supplementary Cementitious Materials (SCMs) was not considered. Therefore, the evolution of the design codes led to an unintentional reduction in embodied carbon between the CP114 code and the Eurocodes.