What makes a building earthquake-resilient?
Earthquakes are one of the most destructive natural disasters in the world! They are aptly dubbed a disaster as they destroy cities, buildings, communities, lives, and cost literally billions to repair the damages. Often a lot of earthquake casualties are not caused precisely by the earthquake itself, but more commonly people being trapped and crushed inside fallen structures.
Our Nation was struck hard on February 22nd, 2011 when Christchurch was hit with a 6.3 magnitude earthquake, killing 185 people and injuring thousands. The city was transformed into a shell of what it once was. Since this tragedy, New Zealand engineers and designers have been placing more emphasis on creating earthquake-resilient buildings. The Superhome movement advocates that to have a truly ‘super’ structure it should have earthquake-resilient foundations.
Generally, buildings are built to withstand the vertical forces placed upon them from their physical weight and gravity. However, when an earthquake occurs, it forces the building to move in a horizontal fashion, due to the moving tectonic plates beneath the Earth’s surface. This ‘unnatural’ movement for the building causes the supporting framework to rupture and, in some cases, for the entire structure to collapse.
Let’s take a look at what design elements and techniques can be used to help create an earthquake resilient building
Create a better foundation systems.
Heavier frame building like commercial/industrial building can incorporate systems of flexibility in the primary structure to the foundations. All reinforcing post earthquake, was upgraded to a more ductile type which meant it was able to stay connected without shearing and failing.
For a lighter building like homes, stiff foundation system provides the best performance. All foundations in earthquake prone areas require professional collaboration with a specialist in geotech and structural engineering. While soils can and will move and slump during these future events it is vital that our homes are robust and resilient by use of better design.
Similar to that of the shock absorbers in your car, this technique, also known as ‘damping’ can be used to help manage the effects of an earthquake. This can be done in 2 ways; pendulum power and vibrational control devices.
This is more commonly used for skyscrapers or alike. A large weights used in conjunction with hydraulics to counter the directional shift of the earthquakes movements, to keep the building upright.
Vibrational control devices
These can be placed throughout the structure of the building, in some cases at every level. This method uses pistons and oil to convert the felt effects of the earthquake from movement to heat! The building would still shift of course, but there is less force being placed upon the areas where these vibrational control devices are situated.
Shield buildings from vibrations
This design element utilises thousands of plastic rings around the building, beneath the Earth’s foundations. When an earthquake occurs, the seismic waves travel along these plastic channels and therefore help to minimise the effects of the building encountering the earthquake motion in the first place!
The materials you use are key in helping to make a building earthquake resilient. What’s that saying? “Bend but don’t break?” When selecting materials you want to use elements that have high ductility. That is, the ability to bend but not break. Structural steel and certain types of wood have high ductility. There are also newer materials that are being utilised more in earthquake-prone regions such as memory alloy and bamboo.
Earthquakes literally shatter the world that we live in. They can:
- Take our loved ones away
- Disrupt family homes
- Close down businesses
- Cause people to live in sub-standard homes years after the event due to insurance and cost challenges
Having a strong earthquake-resilient home can literally save lives and businesses, decrease mental health issues from arising in the occupants, and save you and your insurance provider money.
A strong foundation is the first step to ensuring a safe, long-lasting space for everyone. If investing in safety is important to you, reach out to us before you start your next build!