Earthquake caused due to the seismic waves created due to sudden release of energy in the Earth’s Lithosphere, strong enough to propel objects and people and wreck destruction across entire cities.
Earthquakes have been a major threat to human lives and the infrastructure as a whole. An earthquake leaves behind a catastrophic result causing severe damage to lives.
Over the years efforts have been made to avoid these catastrophic effects of the earthquake. However, it is not possible to construct a building that is completely earthquake proof. Engineers have found various ways to cut down the effects on seismic waves subjected to the building.
These methods have proved to be efficient to a great extent resulting in preserving numerous valuable lives as well as infrastructure.
However, the earthquake resisting methods applied to the buildings depends on how frequent earthquake takes place in an area. The areas prone to frequent earthquake have to adopt exclusive methods as compared to that of the areas which experience less frequent earthquakes.
New designs and new construction materials have been introduced by engineers. Here are some of the methods to make a building Earthquake resistant.
1. Create a flexible foundation
By lifting the building’s foundation, the ground forces can be resisted. Base isolation involves construction of building on top of flexible pads made of steel, rubber and lead. As the base moves during the earthquake, the isolators vibrate while the structure itself remains steady. This effectively helps to absorb seismic waves and prevent them from traveling through a building.
2. Counter Forces with Damping
In this method shock absorbers are used to reduce the magnitude of shockwaves. This mechanism is also used in cars, which are used as shock absorbers. This is done in two ways; Vibration control devices and pendulum dampers.
Vibration Control Devices
In this method, dampers are placed at each building level between column and beam. These dampers consist of piston heads inside a cylinder filled with silicone oil. On occurrence of earthquake, the building transfers the vibration energy into the pistons, pushed against the oil. Furthermore, this energy is transformed into heat, dissipating the force of the vibrations.
This method is mostly used in skyscrapers. A large ball is suspended with steel cables with a system of hydraulics at the top of the building. The ball acts as a pendulum on the occurrence of the earthquake, which makes the ball to move in the opposite direction to stabilize the direction.
3. Shield Building from Vibrators
Researchers are experimenting with ways buildings can deflect the energy from earthquakes. This method is also known as “seismic invisibility cloak”, which involves creating a cloak of 100 concentric plastic and concrete rings in and burying it at least three feet beneath the foundation of the building.
The seismic waves are redirected to move through the outer rings for easier travel, which as a result, channels the waves away from the building and dissipates into the plates in the ground.
4. Reinforce the Building Structure
Buildings need to redistribute the forces that travel through them during a seismic event. Shear walls, cross braces, diaphragms and moment-resisting frames are central to reinforcing a building. Shear walls efficiently transfers the earthquake forces.
These walls are made of panels, which help a building keep its shape during movement. These walls are supported by a diagonal cross braces. These steel braces have the ability to support compression and tension, which helps to counteract the pressure and push forces back to the foundation.
Moment resisting frames provide more flexibility in a building’s design. It is placed among the joints of the building and allows for the columns and beams to bend while the joints remain rigid.