Understanding and Reducing Overdesign in Structural Engineering

Climate change was declared a climate emergency by the UK Parliament in 2019. The Institute of Structural Engineers (IStructE) followed this declaration with the creation of the Climate Emergency Task Group (CETG) and since then have highlighted the responsibility of the structural engineer in tackling this climate emergency through publications, magazine articles and seminars. For example, a recent IStructE publication, Design for zero, stated that structural engineers need to "make carbon as important as safety in our calculations".

Research shows that overdesign is common in structural engineering, from the use of imposed loads that are higher than recommended by the Eurocode, to a utilisation factor of 0.8 being typical. Research suggests that some of this overdesign comes from design uncertainty, concerns about quality assurance onsite, and a potential lack of understanding of structural behaviour. Some overdesign is unavoidable, a utilisation factor of exactly 1 is difficult to achieve - for example, the required area of steel in a reinforced beam will likely have to be rounded up based on available bar dimensions. However, structural engineers need to be aware of the carbon impact of design decisions and avoid unnecessary overdesign.

This research aims to understand the causes of overdesign and consider ways to reduce the level of overdesign that takes place. To achieve this aim, individuals who influence structural engineering design and construction decisions will be interviewed to determine what they consider overdesign, why they think overdesign occurs and if the declaration of the climate emergency has changed their approach to design decisions. This qualitative analysis will be carried out to inform the questions for a larger quantitative study.

From the analysis of the findings, potential solutions to some of the identified causes will be investigated.