Technologies That Help Buildings Resist Earthquakes

Sunday, December 10, 2017 - 11:11

Today, we are very susceptible to the aftereffects of powerful earthquakes. When exposed to the sudden lateral forces produced by seismic waves, even modern buildings and bridges can fail completely and collapse, crushing the people in, on and around them.

Due to the last few decades, architects and engineers have devised a number of clever technologies to ensure that houses, multidwelling units and skyscrapers bend but don't break, Science reports.

Here is the list of 10 temblor-thwarting technologies which some have been around for several years. Others, like the first item, are relatively new ideas that are still being tested.

10. The Levitating Foundation: this concept relies on separating the substructure of a building from its superstructure. One such system involves floating a building above its foundation on lead-rubber bearings, which contain a solid lead core wrapped in alternating layers of rubber and steel. Steel plates attach the bearings to the building and its foundation and then, when an earthquake hits, allow the foundation to move without moving the structure above it.

9. Shock Absorbers: It slows down and reduces the magnitude of vibratory motions by turning the kinetic energy of your bouncing suspension into heat energy that can be dissipated through hydraulic fluid. In physics, this is known as damping, which is why some people refer to shock absorbers as dampers.

8. Pendulum Power: Damping can take many forms. Another solution, especially for skyscrapers, involves suspending an enormous mass near the top of the structure. Steel cables support the mass, while viscous fluid dampers lie between the mass and the building it's trying to protect. When seismic activity causes the building to sway, the pendulum moves in the opposite direction, dissipating the energy.

7. Replaceable Fuses: Researchers from Stanford University and the University of Illinois introduced vertical cables that anchor the top of each frame to the foundation and limit the rocking motion. Not only that, the cables have a self-centering ability, which means they can pull the entire structure upright when the shaking stops. The final components are the replaceable steel fuses placed between two frames or at the bases of columns. The metal teeth of the fuses absorb seismic energy as the building rocks. If they "blow" during an earthquake, they can be replaced relatively quickly and cost-effectively to restore the building to its original, ribbon-cutting form.

6. Rocking Core-wall: Researchers have found that fixed-base buildings with core-walls can still experience significant inelastic deformations, large shear forces and damaging floor accelerations. One solution, involves base isolation -- floating the building on lead-rubber bearings. This design reduces floor accelerations and shear forces but doesn't prevent deformation at the base of the core-wall.

A better solution for structures in earthquake zones calls for a rocking-core wall combined with base isolation. A rocking core-wall rocks at the ground level to prevent the concrete in the wall from being permanently deformed. To accomplish this, engineers reinforce the lower two levels of the building with steel and incorporate post-tensioning along the entire height. In post-tensioning systems, steel tendons are threaded through the core wall. The tendons act like rubber bands, which can be tightly stretched by hydraulic jacks to increase the tensile strength of the core-wall.

5. Seismic Invisibility Cloak: the "seismic invisibility cloak" for its ability to render a building invisible to surface waves. Engineers believe they can fashion the "cloak" out of 100 concentric plastic rings buried beneath the foundation of a building. As seismic waves approach, they enter the rings at one end and become contained within the system. Harnessed within the "cloak," the waves can't impart their energy to the structure above. They simply pass around the building's foundation and emerge on the other side, where they exit the rings and resume their long-distance journey. A French team tested the concept in 2013.

4. Shape Memory Alloys: Many engineers are experimenting with these so-called smart materials as replacements for traditional steel-and-concrete construction. One promising alloy is nickel titanium, or nitinol, which offers 10 to 30 percent more elasticity than steel [source: Raffiee]. In one 2012 study, researchers at the University of Nevada, Reno, compared the seismic performance of bridge columns made of steel and concrete with columns made of nitinol and concrete. The shape memory alloy outperformed the traditional materials on all levels and experienced far less damage [source: Raffiee].

3. Carbon-fiber Wrap: Manufacturers produce these wraps by mixing carbon fibers with binding polymers, such as epoxy, polyester, vinyl ester or nylon, to create a lightweight, but incredibly strong, composite material. Engineers simply wrap the material around concrete support columns of bridges or buildings and then pump pressurized epoxy into the gap between the column and the material.

2. Biomaterials: MIT scientists believe that it's the dynamic response of the natural material under heavy strain that makes it so unique. When researchers tugged and pulled on individual strands of spider silk, they found the threads were initially stiff, then stretchy, then stiff again. It's this complex, nonlinear response that makes spider webs so resilient and spider thread such a tantalizing material to mimic in the next generation of earthquake-resistant construction.

1. Cardboard Tubes: Even cardboard can become a sturdy, durable construction material. Japanese architect Shigeru Ban has designed several structures that incorporate cardboard tubes coated with polyurethane as the primary framing elements. In 2013, Ban unveiled one of his designs -- the Transitional Cathedral -- in Christchurch, New Zealand. The church uses 98 giant cardboard tubes reinforced with wooden beams [source: Slezak]. Because the cardboard-and-wood structure is extremely light and flexible, it performs much better than concrete during seismic events. And if it does collapse, it's far less likely to crush people gathered inside. All in all, it makes you want to treat the cardboard tubes nestled in your toilet paper roll with a little more respect.

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