Throughout history, human beings have built impressive structures and cities that can only be tested with the forces of nature. The most dangerous of these forces of nature is undoubtedly the earthquake. Seismic waves on the ground can destroy buildings and take lives.
The destruction caused by the earthquake also causes enormous costs. According to the US National Earthquake Information Center, an average of 20,000 earthquakes occur each year;
Although the majority are unnoticeably low in severity, those that cause major disasters continue to take lives in any corner of the world. For example, in September 2017, a 7.1 magnitude earthquake rocked the Mexican capital and killed about 230 people.
As in otherearthquakes, the damage was not caused by the earthquake itself, but by the collapse of the people inside the buildings. Of course, this fact necessitates earthquake- resistant buildings.
Over the past few decades, engineers have introduced new designs and construction materials to better equip buildings to withstand an earthquake. But first, it is important to understand how earthquakes affect man-made structures. When an earthquake occurs, short shock waves occur at different intervals throughout the earth.
Buildings are generally designed to carry vertical forces, that is, forces from their own weight and gravity, so they have difficulty resisting side forces emitted by earthquakes.
This horizontal load vibrates walls, slabs, columns, beams and connectors that hold them together. The difference in motion between the top and bottom of buildings can exert excessive pressure, leading to breakage of the support frame and collapse of the entire structure.
How to Build an Earthquake Resistant Structure?
To
design an earthquake-resistant building, engineers must strengthen the structure and prevent earthquake forces. Since earthquakes release energy that pushes a building in one direction, the strategy is to push the building in the opposite direction.
In this paper, we tried to examine some of the methods used to help buildings withstand earthquakes.
Flexible Foundation
One way to resist the land forces is to “lift up” the foundation of building from ground. Floor insulation includes building a structure on flexible pads made of steel, rubber and lead. When the base moves during an earthquake, the insulators vibrate and the structure itself remains constant.
This effectively helps to absorb seismic waves and prevent them from moving through the building.
Damped Counter Forces
Almost everyone knows that vehicles have shock absorbers, but most people do not know that they are also used to build earthquake resistant buildings. Similar to their use in automobiles, the shock absorbers reduce shock waves and help slow down buildings.
This is achieved in two ways: vibration control devices and pendulum dampers.
Vibrating Controllers
The first method involves placing dampers between a column and beam at each level of a building. Each damper consists of piston heads in a cylinder filled with silicone oil. When an earthquake occurs, the building transfers its vibration energy to the pistons and pushes it against the oil.
Energy is transformed into heat by dissipating the power of vibrations.
Pendulum Strength
Another damping method is the pendulum power used primarily in skyscrapers. Engineers suspend a large ball with steel cables with a hydraulic system at the top of the building. When the building starts to shake, the ball acts as a pendulum and moves in the opposite direction to balance the direction.
Like damping, these features are set to match and balance the frequency of the building in the event of an earthquake.
Hiding Buildings from Vibrations
Researchers are experimenting with methods that buildings can divert and direct energy from earthquakes, rather than just opposing forces. This innovation, called “seismic invisibility cloak içer, involves creating a cloak of 100 concentric plastic and concrete rings and burying them under the foundation of the building.
When seismic waves reach these rings, they are forced to pass to the outer rings. As a result, it is substantially channeled away from the building and distributed to the floor plates.
Strengthen the Structure of the Building
To withstand demolition, buildings must redistribute the forces passing through them during a seismic event. Shear walls, beams, diaphragms and moment-resistant frames are central to reinforce a building. Shear walls are a useful building technology that helps to transmit earthquake forces.
These walls made of panels help a building to maintain its shape during movement. Shear walls are generally supported by cross-brackets. These steel beams are capable of supporting compression and tension which help to prevent pressure and push forces back to the foundations.
Diaphragms are a central part of the structure of a building. The diaphragms of the building’s are horizantal surfaces such as floors, roof and decks take the tension from the floor and directs this power to the vertical structures of the building. Moment resisting frames provide greater flexibility in the design of a building.
This structure is placed between the joints of the building and allows the bending of the columns and beams while the joints remain rigid. Thus, while the building can withstand the greater forces of earthquakes, it gives designers more freedom to arrange building elements.
Earthquake Resistant Materials
Shock absorbers, pendulums and “invisibility cloaks olabilir can help to a certain degree of energy dissipation, while materials used in a building are equally responsible for their stability.
Steel and Wood
A building material must have high ductility to withstand stress and vibration - the ability to be exposed to large deformations and stresses. Modern buildings are often constructed with structural steel - a steel component that comes in a variety of ways to allow buildings to bend without breaking.
Wood is a surprising ductile material due to its high strength compared to its light structure.
Innovative Materials
Scientists and engineers are developing new building materials that are capable of further shaping. Innovations such as shape-memory alloys are both capable of withstanding heavy stress and return to their original shape, while fiber-reinforced plastic packages made by various polymers can wrap around columns and provide 38% more strength and ductility.
Engineers are also turning to natural elements. Adhesive but solid mussel fibers and spider thread strength / aspect ratio have promising capabilities in forming structures.
Bamboo and 3D printed materials can also function as lightweight, interlocking structures in unlimited ways, potentially providing greater resistance to buildings.
References:
• https://science.howstuffworks.com/engineering/structural/earthquake-resistant-buildings.htm
• http://www.reidsteel.com/steel-buildings/resilient-steel-structures/earthquake-resistant-building/
• https://www.rishabheng.com/blog/earthquake-resistance-design-techniques-for-civil-structure/
• https://www.viatechnik.com/science-behind-earthquake-proof-buildings/
• https://interestingengineering.com/top-5-earthquake-resistant-structures-around-world
• https://tommytoy.typepad.com/.a/6a0133f3a4072c970b01538e0889f1970b-600wi
• https://www.kansascityfed.org/publications/research/oke/articles/2016/economic-damage-large-earthquakes
• https://www.nationalgeographic.com/environment/natural-disasters/earthquakes/
• https://www.bigrentz.com/blog/earthquake-proof-buildings
