A New Coating to Protect Buildings from Earthquakes
The innovative material, simply sprayed onto walls, can retrofit even older buildings to protect them against earthquakes.
The powerful tremors that devastated Mexico recently reminded us about the frailty of human buildings when facing natural forces without the proper protection protocols. Japan learnt this the hard way back in 1995, when the Kobe earthquake tragically killed more than 5,000 people. This event would become a tipping point for the construction of earthquake-proof buildings. In fact, in 2011, when the country suffered a 9.0 earthquake, most of the modern structures were able to resist the tremors. However, it is not always feasible to put such stringent measures into place, as older buildings would have to be demolished to make way for the new ones. That is, until new technologies arrive, such as that developed by professor Nemkumar Banthia and his team at the British Columbia University.
The new material created under the tutelage of this civil engineering professor has been called EDCC (Eco-friendly Ductile Cementitious Composite) and simulations have shown it to resist forces as powerful as those unleashed in the 2011 Japanese earthquake. The best thing about it is how easily it can be applied – basically spraying it onto a wall to achieve a 10 mm-thick coating. “This is sufficient to reinforce most interior walls against seismic shocks”, Soleimani-Dashtaki, one of the researchers, explained.
To provide this kind of protection, the material makes use of a mixture of polymer-based fibres, fly ash and other industrial additives. In fact, 70% of the usual cement is replaced by the aforementioned fly ash, which is a by-product from coal-burning power stations. This means that the amount of cement needed is substantially reduced and, with it, the emission of carbon dioxide. It should be remembered that producing a ton of cement generates almost as much carbon dioxide. That’s where the eco-friendly label comes into play.
EDCC is no pie in the sky, as earthquake prevention retrofitting measures are already being implemented in buildings from the British Columbia University campus and are planned for the Dr. Annie B. Jamieson Elementary School in Vancouver. It is expected to play a significant role in the near future for the strengthening of pipelines, pavements, offshore platforms, blast-resistant structures, and industrial floors.
Other earthquake protection techniques
Research during the last few decades has brought significant progress in the field of earthquake damage prevention. As mentioned earlier in this article, Japan is one of the leading countries in this area, but there are other nations, such as Chile, that have also implemented innovative construction protocols to tackle these issues. A great deal of the progress made is related to the understanding of a natural phenomenon called liquefaction, by which the bedrock on which the foundations of the building rest behaves as a liquid when exposed to huge geological forces such as those of earthquakes.
These are some of the most frequent techniques to safeguard buildings from earthquake damage:
- Structure flexibility. One of the key elements is to achieve a certain degree of flexibility in the concrete and steel structures to avoid breakage. It is as if the whole building waltzes along in time with the earthquake instead of the dancers treading on each other’s feet. For instance, in Japan beams are intertwined to behave like knots. Steel sheets covered by latex membranes are also used.
- Compensating pendulums and mass dampers. The collapse of a skyscraper is a truly devastating event to be avoided at all costs. That’s why a heavy structure is placed on the top of some tall buildings which behaves like a counterweight in the event of seismic tremors. If the building leans to the left, the counterweight will move to the right, and the other way round. An example of this kind of mechanism can be found on the Taipei 101, a 1,600 feet tall skyscraper in Taiwan, China.
- Seismic isolation and energy dissipation systems. The former are used to decouple the building from the bedrock where it’s placed. In that way, movement just affects the actual isolation system and not the building above. Just imagine a waiter keeping a tray static in the air while moving the rest of his body. The latter, on the other hand, operate as dampers that absorb the lateral movement of the building.