Earthquakes are among the most destructive forces on earth. The seismic forces running through the ground can take lives. It can destroy buildings, and leave unsurmountable loss at its wake.
According to records, the US expects about sixteen major earthquakes each year. Out of these sixteen earthquakes, fifteen are in the magnitude of seven on the Richter scale. But one has a magnitude of eight or higher.
The effects of earthquakes are still as devastating as they have always been. Yet, the new designs and techniques introduced by engineers have better-equipped buildings to withstand the tremors.
Here’s A Closer Look At How Buildings Are Designed Today To Survive Earthquake Loads.
1. Creating a Flexible And Robust Foundation
Earthquakes make the base of the building move, while the structure stays steady. The building’s foundation has to be lifted above the earth to resist the ground forces.
Buildings are made over flexible pads made of lead, rubber, and steel to ensure base isolation. The isolators vibrate as the earthquake makes the base move. But the structure stays steady. It helps in effectively absorbing seismic waves and preventing them from travelling through the buildings.
2. Using Damping to Counter Seismic Forces
You are aware that cars come with shock absorbers. But you might not know that they are also used to make earthquake-resistant buildings. The shock absorbers for buildings reduce the impact of the shockwaves in two ways. These are pendulum dampers and vibrational control devices.
● Pendulum Dampers
Pendulum dampers are useful mainly for the skyscrapers. The engineers use a hydraulic system to suspend a huge ball having steel cables from the top of a building. As the building starts swaying, the ball starts acting as a pendulum. To make the direction stable, it goes in the opposite direction. As a result, it matches and counteracts the frequency of the building when an earthquake occurs.
● Vibrational Control Devices
Engineers place dampers at every level of the building between a beam and column. Every damper includes a cylinder full of silicone oil and piston heads inside it. At the time of an earthquake, the vibrational energy gets transferred into the pistons, which push against the oil. The transformation of the energy into heat dissipates the vibrational forces.
3. Protecting Buildings from the Vibrations
Reports suggest that nearly 75% of deaths in an earthquake is the result of structural collapses. Researchers are focusing on completely deflecting and rerouting the energy from the earthquakes, instead of counteracting forces.
The innovative method of using a seismic cloak depends on creating a layer of a hundred concentric concrete and plastic rings and burying it all at least three feet below the building’s foundation.
When seismic waves go inside the rings, they pass through the outer rings. This way, they can travel easily. Due to this, they get channelled away from the building and dissipate in the ground.
4. Reinforcing the Structure of a Building
Buildings have to dissipate the seismic forces travelling through them during an earthquake. This way, they can survive the collapse. Cross braces, shear walls, moment-resisting frames, and diaphragms can reinforce buildings.
● Braces and Shear Walls
Shear walls are immensely helpful in transferring earthquake forces. These walls are of panels and help the building hold its shape even during movement. Diagonal cross bracing is ideal for supporting the shear walls. These are steel beams that have the capability of supporting tension and compression. This aids in neutralizing the pressure as a result of which the forces return into the foundation.
Diaphragms are a crucial part of the structure of a building. It consists of the building’s floors, the decks kept over them, and the roof. Diaphragms play a vital role in getting rid of the tension from the floors. They also push force to the building’s vertical structures.
● Moment-Resisting Frames
Moment-resisting frames are imperative to bring more flexibility to the design. The frames are put among the building’s joints. It lets the beams and columns bend while the joints stay rigid. It also helps the building resist the force of an earthquake. Thus, designers get greater freedom in arranging building elements.
5. Using Earthquake-Resistant Building Material
All the methods mentioned above help in dispelling the seismic energy to some extent. Yet, the stability of a building also comes from the materials used in it.
Wood and Steel
High ductility is a crucial component to have in building material to resist vibration and stress. Ductility refers to the ability to undergo large tensions and deformations.
Structural steel is often used in modern constructions. It lets the buildings bend without getting damaged. Steel cladding is useful in making the roof light, which can prevent collapsing of the building to a great extent. Wood is also highly ductile because of its strong but lightweight structure.
Engineers and scientists are creating new-age building materials. These have an even greater ability to retain their shapes. Innovations such as shape memory alloys can endure heavy forces and keep their actual shapes.
On the other hand, fibre-reinforced plastic wraps can increase ductility and strength. Columns are wrapped with these wraps of polymers.
You can use it both in the ceiling and wall for reinforcing the building structure. It will help you withstand not only earthquakes but also other natural calamities.
The advanced materials and technology have already withstood earthquakes to a considerable extent. But, resisting a powerful earthquake has still not been possible by modern construction technology. If the building stands long enough for its occupants to evacuate, you can still consider it a great success.