Modern buildings are built to fire safety standards, and structures located in seismic zones must also be able to withstand earthquakes. But the effects of climate change are also increasing the threat to buildings, not just from floods or other sudden natural disasters, but from global warming itself, which is now affecting buildings and other infrastructure in ways that experts are only beginning to understand.
For decades, scientific studies and assessment reports by the UN’s Intergovernmental Panel on Climate Change (IPCC) have warned of changes in the Earth’s dynamics due to global warming, and observations have confirmed an increase in extreme weather events leading to major natural disasters. There is also growing evidence that small geological perturbations caused by climate change can be the final straw, triggering volcanic eruptions, earthquakes and tsunamis.
Making buildings resistant to natural disasters is nothing new. Earthquakes are the most classic case; in ancient Japan, for example, wood was the preferred building material to give structures greater lightness and elasticity to withstand the effects of strong shaking. Today, near the Japanese city of Kobe, the world’s largest earthquake simulator is used to study the effects of earthquakes on replicas of entire buildings. Meanwhile, in certain coastal areas and countries such as the Netherlands, building on stilts to prevent flood damage has a long tradition, while other techniques for living with floods include floating buildings and the use of waterproof materials and designs.
Other, more audacious ideas are designed to protect buildings from volcanic eruptions by placing them on titanium or tungsten stilts to withstand lava flows, and roofing them so that volcanic ash slides right off. Japan’s Fukushima nuclear power plant, like others in the country, had a wall to protect it from the sea, but it was not high enough to contain the tsunami that caused the 2011 disaster. Other ideas include designing buildings with a hydrodynamic shape to withstand catastrophic ocean waves.
Urban heat islands
While these are the most obvious threats, they are not the only ones that buildings will face as climate change worsens. We have all heard of urban heat islands, which can make cities almost 4 °C warmer than surrounding rural areas. But this heat not only affects the air, it also penetrates the ground beneath our feet, creating subsurface heat islands, to which underground infrastructure such as tunnels, car parks, basements and sewers also contribute. Several studies have analysed the impact of this ground warming on, for example, aquifers.
We now know that underground climate change, whose effects are mostly hidden from view, can damage buildings. At Northwestern University in Illinois, engineer Alessandro Rotta Loria studies how this underground heat is affecting the foundations of Chicago. The city of skyscrapers is criss-crossed by tunnels that carry vehicular and pedestrian traffic. In the business district surrounded by the elevated railway known as the Loop, Rotta Loria and his team installed a network of 150 temperature sensors. The data collected over three years was fed into a simulation model to analyse how ground temperatures have changed since 1951, when the tunnel network was completed, how they will evolve until 2051 and how this will affect ground deformation.
The results show that subsurface temperatures in the Loop are up to 10 °C higher than under Grant Park on the shores of Lake Michigan, that between different soil layers and areas in the centre they can vary between 1 °C and 5 °C, and that overall they are increasing at a rate of 0.14 °C per year. What’s more, the air in the subsurface is warming by up to 25 °C above normal. All this heat is deforming the ground and the structures embedded in it, causing displacements of up to 12 millimetres and producing possible cracks. “These deformations and displacements are significant and, on a case-by-case basis, may be incompatible with the operational requirements of civil structures,” Rotta Loria writes in his study.
According to the engineer, buildings were not designed to withstand this “silent hazard”, and soils such as Chicago’s exacerbate the problem: “Chicago clay can contract when heated, like many other fine-grained soils. As a result of temperature increases underground, many foundations downtown are undergoing unwanted settlement, slowly but continuously. In other words, you don’t need to live in Venice to live in a city that is sinking—even if the causes for such phenomena are completely different”. However, he clarifies that the problem is not unique to Venice: “All urban areas suffering from underground climate change are prone to have problems with infrastructure”. He adds: “European cities with very old buildings will be more susceptible to subsurface climate change”.
“Although this phenomenon is not dangerous for people’s safety necessarily, it will affect the normal day-to-day operations of foundation systems and civil infrastructure at large,” explains Rotta Loria. His study is the first to quantify these effects, but the engineering community has been commenting for years on the need to incorporate resilience to the impacts of climate change in construction, as its consequences are still unpredictable.
Rotta Loria points to a solution that is already being considered: how this surplus heat can serve as a source of green energy to heat homes, similar to other strategies for underground thermal energy storage, without the need to produce the heating, as it occurs spontaneously in this case. The engineer adds that underground structures could be thermally insulated. But, in the end, all roads lead to the same conclusion: “The ongoing underground climate change should be mitigated to avoid unwanted impacts on civil structures and infrastructures in the future”, he concludes.
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