Earthquakes can cause devastating damage to homes and buildings, causing countless injuries and even death. Making buildings safer from these disasters is of prime importance in many areas of the world. Earthquake proof construction materials and techniques can be implemented and help prevent property damage and injury. These techniques are based on either strengthening the structure of the building or redirecting or dissipating the seismic waves so they don’t affect the building’s structure.
What is meant by “earthquake proof?”
Buildings are designed to handle the vertical pressures from gravity and the weight of the materials and occupants inside them. They are not, however, designed to withstand the horizontal forces that are placed on them during an earthquake. Earthquake proof buildings must be designed with these horizontal forces in mind.
The goal of earthquake proofing is to design and construct a building that is able to withstand the ground shaking that occurs during an earthquake, minimizing structural damage and preventing deaths and injuries. Although the term “earthquake proof” is commonly used, a more accurate way to describe this type of construction may be “earthquake resistant,” as no structure can be completely immune from the sudden shaking caused by these phenomena.
Earthquake proof building design
In earthquake prone areas of the world, building codes require that structures meet certain requirements to help protect buildings and their occupants. Many of the techniques below are used to help make buildings more resilient.
Reinforced structure
One of the most common ways to prevent damage and protect buildings and occupants is to provide a reinforced structure that can withstand the horizontal stresses caused by shaking. Shear walls, cross braces, diaphragms, and moment-resisting frames are used to redistribute the energy safely, without major structural damage.
Shear walls are made up of multiple panels and are usually cross braced for extra support. Diaphragms, like a building’s floors, roof, and decks, disperse the energy to the vertical components of the building, which are stronger. Moment frames allow beams and columns to bend while their joints stay rigid, providing flexibility to help keep the structure sound.
Flexible foundation
Relatively new technology and design ideas involve constructing the building’s foundation in such a way so that it is able to vibrate with the motion of the ground while the building itself stays in place. This technology is called base isolation, and it involves constructing a building on top of flexible pads. During an earthquake the base moves and the isolators vibrate while the structure itself remains in place above ground. This helps absorb seismic waves and prevents them from traveling through and damaging the building.
Shock absorbers
Much like the shock absorbers on a car, new technology is installing them in buildings. The technique requires two pieces: absorbers and a pendulum. Piston absorbers are installed on every floor on the beams and columns and they transfer the vibrational energy into heat. Then a large ball is suspended from steel cables that connect to a hydraulic system at the top of the building (this is usually done in skyscrapers). As the building begins to sway, the ball moves in the opposite direction of the horizontal shaking and stabilizes the building.
“Seismic invisibility”
No, this is not some magic out of a book about wizards. New research is looking at the ways buildings can deflect and reroute energy, creating less stress on the structure. This new technique, called the “seismic invisibility cloak,” involves burying 100 concentric plastic and concrete rings at least 3 feet beneath the foundation of the building. When the ground shakes, these rings direct the energy out from the building and dissipate it, leaving the building mostly untouched.
Materials used in earthquake proof buildings
The most important feature of materials used in earthquake proof buildings is ductility. Ductility is the ability of a material to deform without failure. Materials like steel, lumber, and bamboo have high ductility, so they are often used in these types of buildings. Materials like brick and concrete have poor ductility, so they aren’t as good to use in these structures.
In addition, scientists have developed some new metals and plastics that can help make buildings safer during earthquakes. Shape memory metal alloys retain their shape even under high stress, and fiber reinforced plastic wrap can be used to protect structural elements, providing additional strength and ductility.
The latest in earthquake proof building technology
In the last few years science has made some real advancements in earthquake protection technology. From building shock absorbers to spider silk, scientists are leaving no stone unturned in the search for better building materials and techniques.
Base isolators
Base isolation pads serve to separate a building’s structure from its foundation, allowing them both to move independently. During an earthquake, the foundation shifts side to side while the structure above the ground remains in place. The isolating pads, which are made out of steel, rubber, and lead, protect the building from seismic waves, keeping it intact.
Movement dampers
Piston dampers, consisting of piston heads inside a silicone oil filled cylinder, are installed on the beams and columns on each floor. During an earthquake, the vibrational energy is transferred into the pistons, which push against the oil. In this way, the energy is transformed into heat and the force of the vibrations is dissipated.
Mussel fibers and spider silk
We learn so much from Mother Nature, and scientists are looking at different mussel fibers and spider silk for clues to strengthen materials. In particular, they are focusing on the sticky, rigid nature of the fibers of mussels, and the strength-to-size ratio of spider silk. In the near future materials augmented with these natural materials may save lives in earthquake prone areas around the world.
Ductile cementitious composite
This eco-friendly coating could be the key to strengthening existing buildings and making materials like brick and concrete better at resisting horizontal stress. Ductile cementitious composite is a fiber reinforced material with properties similar to steel. Scientists have shown that applying a 10-millimeter-thick layer of this material to interior walls protected them from damage during a 9.0-magnitude simulated earthquake.
With new materials and technologies, scientists and engineers hope to provide more protection for those living in earthquake prone areas. These materials and techniques will become even more valuable as we run out of bare land and continue to build taller and taller buildings.
