Standing on solid ground is a well-known saying that indicates that things are stable and standing still. If that term applies on people, it surely applies on buildings that hold hundreds and maybe thousands of lives inside of them. Earthquakes are not a thing of man-doing, it is a natural hazard that is unavoidable by all means. However, avoiding the aftermath is absolutely doable and in human hands by designing buildings that are earthquake resistant. Before dwelling into the technologies and the techniques to apply for constructing an earthquake-proof building, let’s explain how earthquakes do happen.
The story between a small crack and an earthquake
An earthquake is a result of an energetic pulsation coming from deep layers in the ground, sending vibrations to the upper layers and eventually shaking whatever is on the surface. Scientifically, these vibrations are called seismic waves which are waves of energy caused by the sudden breaking of a rock within the earth or an explosion. There are several types of waves and they all move in different ways, but the two main types of waves are body waves and surface waves. The body waves travel through the interior of earth and are known to have higher frequency compared to surface waves which travel only through the surface and moves horizontally, commercially known as love wave.
Man-made structures are equipped to deal with vertical forces from their weight and gravity, whereas they can not handle side-to-side forces caused by earthquakes. In fact, our planet seems to be still but it is on a constant move, the surface is based on enormous pieces of rock that are very slowly moving. When those pieces move slightly harder and rub against one another, the edges slip and release huge amounts of energy causing earthquakes.
What should engineers do to build earthquake-proof buildings?
- Build with flexibility
Yes, you have read it correct. For a building to resist an earthquake shake, there is one way to do it which is to build the base of the building separated from the part above the ground. As the ground is shaking, the base isolation technique will allow the building to sway few feet to the right or the left within the range of the buffer zones, without moving the main structure.
- Materials matter
When it comes to selecting construction materials, it should be chosen with high levels of care. Each material has its own impact on the building, how to react towards energy waves and its shock absorbance capability. Structural steel, wood, and bamboo are materials that tend to bend without breaking.
- Shock-absorbent techniques
Shock absorbers are not exclusive for car and railways; buildings also can catch a ride with them and reduce the magnitude of shockwaves. This is achievable through two methods. First by implementing vibration control devices that are attached to beams, transferring those vibrations into pistons to create heat that would dissipate the vibration force. Second method would be in the form of pendulum power, it is primarily used in skyscrapers. A hydraulic large ball with steel cables is attached to the top of the building so that when a building sways right the pendulum ball sways left.
- Soft soil or no soil
The geological soil condition has a major effect on the seismic response of the building. Buildings with soft soil are more prone to higher motion reactions than on rocks.
- Defy and deflect waves
One of the key points to consider applying is concrete and plastic rings that shield the building by defying and deflecting the shockwaves. This consists of 100 concentric rings buried at least three feet away from the core foundation of the building.
- Forces readjusted
No-one constructs building with the intention to watch it collapse, but in the case of earthquakes, buildings need to re-distribute forces that travel through them by applying shear walls, cross braces, diaphragms, and moment-resisting frames that keep joints rigid and allowing the whole structure to bend.
Earthquake-proofing technologies in action
- The Taipei 101 – China
Formerly known as the Taipei World Financial Centre, -1,667-foot-high-, is a landmark that is considered to be one of the tallest buildings constructed in 2004 and should definitely be taken as an example. The architects who were responsible for constructing this sky typhoon installed an enormous pendulum ball (730 tons gold plated) in it, to move itself the opposite direction when the building starts swaying.
- The Sabiha Gokcen International Airport – Turkey
A 2-million square-feet structure that is capable of resisting an earthquake with a magnitude of 8.0 can remain fully operational after such incidents. The triple friction pendulum isolators installed in the building support the whole foundation from moving one inch.
- The Petronas Twin Towers – Malaysia
Located in the heart of Kuala Lumpur, the tallest building in 2004 is structurally built to resist earthquakes. You may think that the bridge between the two buildings is built for aesthetic purposes, however its main purpose remains an interesting fact, where it prevents the wind from putting a load on the towers and making it shift smoothly from side to side.
- The Transamerica Pyramid – USA
Built in 1969 within a seismically active region was a definite challenge for engineers. However, a success was recorded in 1989 when a 6.9 magnitude earthquake hit the skyscraper for more than a minute while only the top story swayed almost a foot side-to-side. The reasoning behind it was the reinforcing rods placed at four places each floor, with clearance room between the panels allowing lateral movement. The Pyramid can resist torsional movement and is constructed to take large horizontal base shear forces.
- The Yokohama Landmark Tower – Japan
Located in the Minato Mirai 21 district of the Yokohama city of Japan, is the second tallest building in Japan standing at 972ft high, makes you think it is highly prone to earthquake shakes. You are mistaken as it was built to facilitate earthquake safety measures, due to the fact that it is placed on rollers that prevent it from shaking while employing a mass-damper system to weigh it down with flexibility to bend not to break.
Though earthquakes have terrified many lives for ages, scientists have been researching for the past century to understand the causes behind earthquakes, predict the time of occurrence, or how to measure magnitude. On the other hand, architects and engineers decided to not cry over spilled milk and worked on earthquake resistant technologies, hoping someday all the other construction professionals would follow the same suit of care and innovation.