Earthquakes are one of the important disasters that have caused destruction in many different parts of the world throughout human history and resulted in the collapse of countless buildings. In Turkey, which is an earthquake country, it is absolutely impossible to think of urban planning and structuring independently of the earthquake phenomenon. Therefore, especially in recent years, there has been an increasing awareness of designing and constructing buildings as earthquake-resistant as possible. But what is the way to design a building to be earthquake resistant? Below are some important tips for designing an earthquake resistant building.
How Do Earthquakes Affect Buildings?
In order to understand how a building can be built more earthquake resistant, it is important to understand how and in what way earthquakes affect buildings.
The main reason underlying the damagingness of an earthquake is the short and fast shock waves that spread in all directions, created by the seismic movements that cause the earthquake on the ground. These waves create a movement and shaking in the horizontal direction in all structures connected to the ground. Whereas, buildings are traditionally always equipped to tolerate vertical forces, impacts and weights against gravity and their own mass. Therefore, these horizontal tremors and strong blows can have devastating consequences for buildings. Simply put, walls, floors, columns, beams and the fasteners that hold them together vibrate as a result of horizontal movements; This excessive stress on the structure causes the supporting frame to break and the entire structure eventually collapses.
How Can a Building Be Made Earthquake Resistant?
The basic logic of constructing an earthquake-resistant building is about strengthening the building and creating resistance in the opposite direction to the force released by the earthquake. Let’s take a look at some of the methods used to achieve this durability:
Creating a flexible foundation: One of the ways to make an earthquake resistant building is to resort to a method called base insulation. In such foundations, steel, rubber and lead materials are used to make the base flexible and resistant to seismic movements. Flexibility in the base allows the foundation to respond to seismic movements while the structure itself remains stable during an earthquake. In this way, seismic waves are absorbed by the insulator materials at the base and destructive movements inside the building are prevented.
Damped Counterforces: If you are familiar with shock absorbers used in cars, you may be surprised to learn that engineers also use these shock absorbers in earthquake resistant buildings. Shock absorbers reduce the strength of shock waves and help reduce pressure on the building, similar to their use in cars. This method can be applied in two ways. The first way is to place dampers, consisting of piston heads inside a cylinder filled with silicone oil, between columns and beams in each layer of the building. Thus, during the earthquake, the building transfers the vibration energy to the pistons, the energy is converted into heat and the power of the vibrations is dissipated. The second way is to use a pendulum. In this method, a large ball is suspended from steel cables connected to a hydraulic system at the top of the building. When the building starts to shake, the ballacts as a pendulum and moves in the opposite direction to stabilize the building against seismic waves.
Protecting Buildings from Vibrations: One way to keep a building immune to seismic waves during an earthquake is to deflect or redirect the vibrations from the target, rather than blocking or dampening the waves. In this new technique, called the “seismic invisibility cloak,” a layer of 100 concentric plastic and concrete rings is formed and buried 3 feet below the building foundation. The seismic waves that occur during the earthquake are kept in this layer and directed to the outer rings, so that the effect of the waves is removed from the building.
Strengthening the Structure of the Building: One of the keys to building earthquake-proof buildings is to focus on the entire building structure, not just the foundation. Shear walls, cross braces and diaphragms, which are useful building technologies that can help disperse seismic waves, are some examples of structures that will provide flexibility and resist earthquakes.
What are Earthquake Resistant Materials?
In addition to all these techniques and structures, the materials used in a building are also of vital importance during an earthquake. For example, the use of steel in the building allows the structure to bend and flex without breaking during an earthquake. In the same way, although wood is quite light compared to other building materials, it gives a useful strength to the building.
However, fiber-reinforced plastics and innovative solutions known as “shape memory materials”, which allow the building to flex and return to its original shape after jolts, are indispensable for constructing earthquake resistant buildings. Also, in recent years, the use of some natural materials such as bamboos, mussels with building materials, and inspiration from the strength of natural structures such as spider webs have helped develop new ways to build earthquake-resistant buildings.
With the developing technique and awareness, it is now possible to imagine a near future where the earthquake will not cause any damage to the buildings.