We’re wasting so much steel, Cambridge study finds

The construction industry could slash its carbon emissions by as much as 50% by using just enough steel, not double the necessary amount as is the current practice, a new Cambridge University study has found.

Construction uses half of the 1.5 billion tonnes of steel produced each year and could drastically reduce its carbon footprint by optimising the design of new buildings without any impact on safety. And if buildings are maintained for their full design life and not replaced early the sector’s emissions could in total be cut by around 80%, says a report published today.

We need to see a more sensible use of materials in the construction sector if we are to meet carbon reduction targets– Julian Allwood

To keep labour costs down, the industry regularly uses double the material required by safety codes. Analysis of more than 10,000 structural steel beams in 23 UK buildings found that, on average, the beams were carrying only half the load they were designed for. The results of the study appeared today in the latest issue of the journal, Proceedings of the Royal Society A.

The study authors say that carbon reductions would come from the fact that over a quarter of the steel produced each year is used in the construction of buildings. Demand for steel is increasing rapidly, especially in the developing world, and is expected to double in the coming decades.

The iron and steel industry contributes nearly 10% of total global carbon emissions, which climate change experts recommend be halved by 2050. Coupled with skyrocketing demand from the developing world, drastic action is required if a reduction in the sector’s carbon footprint is to be achieved. One option to achieve this reduction, the authors say, is to design buildings more efficiently.

"Structural engineers do not usually design optimised structures because it would take too much time. Instead they use repetition to decrease the cost of construction," said Dr Julian Allwood of the Department of Engineering, who led the research, which was funded by the UK’s Engineering and Physical Science Research Council (EPSRC). "This leads to the specification of larger steel components than are required."

The researchers found that building designs are exceeding Eurocode Safety Standards by a factor of two and so are unnecessarily using double the amount of steel and concrete needed. "As materials are cheap and structural design time is expensive, it is currently cheaper to complete a design by using safe but considerably over-specified materials," said Allwood.

The authors found as well that many buildings are being designed to last for 100 years but on average are replaced after just 40. By designing for minimum material rather than minimum cost, steel use in buildings could be drastically reduced, leading to an equivalent reduction in carbon emissions, the study concluded. The net result of avoiding over-design and early replacement is that the UK could provide the same amount of built space with just 20% of the materials used now – and therefore 20% of the carbon emissions.

"We need to see a more sensible use of materials in the construction sector if we are to meet carbon reduction targets, regardless of the energy mix used in manufacturing the materials," said Allwood.

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