Designing Earthquake-Proof Buildings
We’ve designed incredible structures and cities throughout history solely for them to experience the forces of nature. Earthquakes are one of the most disruptive forces on Earth. Seismic waves can kill structures across the earth, take lives, and cost enormous amounts of damage and repair money.
Every year, there are a total of 20,000 earthquakes, 16 of which are major disasters, according to the National Earthquake Information Center. A magnitude of 7.1 rocked Mexico’s capital city on September 20, 2017, and killed approximately 230 people. The harm was not caused by the earthquake itself, as was the case with other earthquakes, but by the collapse of buildings with people inside them, making earthquake-proof buildings a must.
Engineers have introduced new designs and construction materials over the past few decades to properly prepare buildings to withstand earthquakes. Read on to learn how earthquake-proof buildings are built today.
Impact Earthquakes Have on Structures
It’s important to understand how earthquakes affect man-made structures before we look at the features. It sends shockwaves all over the ground in fast rapid intervals in all different directions when an earthquake occurs. Although buildings are normally designed to cope with vertical forces from their weight and gravity, the forces produced by quakes can not be controlled side-to-side.
Walls, floors, columns, beams, and the connectors which hold them together are vibrated by this horizontal load. Extreme stress is exerted by the difference in movement between the bottom and top of buildings, causing the supporting frame to crack and the whole structure to collapse.
Designing Earthquake Resistant Buildings
To construct an earthquake-proof building, engineers need to strengthen the foundation and counteract the forces of an earthquake. Since earthquakes emit energy from one direction that moves a building, the strategy is to push the building the opposite way. Here are some of the strategies that are used to help buildings survive earthquakes.
1 Start with a Flexible Foundation
One method of fighting ground forces is to “lift” the base of the building off the surface. Base isolation includes creating a building made of concrete, rubber, and lead on top of flexible pads. The insulators vibrate when the structure itself stays stable as the foundation moves during the earthquake. This helps to absorb seismic waves efficiently and avoid them from passing through a house.
2. Damping Energy with Counter Forces
You may be aware that there are shock absorbers in vehicles. You may not realize, however, that engineers use them for making earthquake-resistant buildings as well. Shock absorbers minimize the magnitude of shockwaves, similar to their use in vehicles, and help buildings slow down. This is done in two ways: systems for vibrational stimulation and pendulum dampers.
Vibrational Control Devices
The first technique includes putting dampers between a column and a beam at each stage of a house. Inside a cylinder filled with silicone oil, each damper consists of piston heads. If an earthquake occurs, the building pushes against the oil, transferring the friction energy into the pistons. The energy is converted into heat and the force of the vibrations is dissipated.
Pendulum control, used mainly in skyscrapers, is another damping process. A wide ball with steel cables with a hydraulic system is suspended by engineers at the top of the house. The ball acts like a pendulum when the building starts swaying and travels in the opposite direction to stabilize the direction. Like damping, these features in the event of an earthquake are calibrated to balance and counteract the frequency of the building.
3. Protect Structures from Vibrations
Researchers are experimenting with ways in which buildings can deflect and redirect the energy from earthquakes altogether instead of only counteracting powers. This invention called the “seismic invisibility cloak” involves the formation and burial of a cloak of 100 concentric plastic and concrete ring at least three feet below the building’s base.
For easier movement, when seismic waves reach the rings, they are forced to pass through to the outer rings. As a consequence, they are channeled away from the building and dissipated into the soil plates.
4. Reinforce the Structure of the Building
Buildings need to redistribute the forces that pass through them during a seismic event to survive a collapse. For strengthening a structure, shear walls, cross braces, diaphragms, and moment-resisting frames are central.
Shear walls are a valuable construction technology that helps to shift the forces of earthquakes. These walls, made of panels, help a building retain its shape during movement. Shear walls are also protected by cross braces on the diagonal. The ability of these steel beams to support compression and stress helps to counteract pressure and drive forces back to the base.
Diaphragms are a central part of the construction of a house. Diaphragms help relieve stress from the floor and push force to the vertical structures of the building, consisting of the building floors, the roof, and the decks built over them.
In a building’s architecture, moment-resisting frames provide more versatility. This device is mounted between the building’s joints and helps the columns and beams to bend while the joints remain rigid. The building is thus capable of resisting the greater forces of an earthquake while giving designers more flexibility to organize building components.
Materials to Make Earthquake Resistant Buildings
Although shock absorbers, pendulums, and “invisibility cloaks” can help to some degree dispel the energy, its stability is equally responsible for the materials used in a building.
Steel and Wood
It must have high ductility, the capacity to undergo significant deformations and strain, for building material to resist stress and vibration. A part of steel that comes in a variety of shapes that allow buildings to bend without breaking, modern buildings are mostly built with structural steel. Wood, due to its high strength compared to its lightweight form, is also a surprising ductile material.
New construction materials with even greater shape preservation are being developed by scientists and engineers. Innovations such as shape memory alloys can both withstand heavy stress and return to their original shape, whereas fiber-reinforced plastic wrap can be wrapped around columns and provide up to 38 percent higher strength and ductility, created by a variety of polymers.
Engineers shift to natural elements, too. In building structures, the sticky but rigid fibers of mussels and the strength-to-size ratio of spider silk have promising capabilities. Bamboo and 3D printed materials may also act as lightweight, interlocking structures with infinite shapes that can provide buildings with even greater resistance.
To construct some successful earthquake-proof structures, engineers and scientists have designed techniques over the years. It is not yet possible for construction to fully survive a strong earthquake unscathed, as advanced technologies and materials are nowadays. Nevertheless, if a building is capable of allowing its inhabitants to escape without collapsing and saving lives and neighborhoods, we should see it as a great accomplishment.