By Emily Newton
When professionals design and construct buildings, they assess how to reduce risks. Following the applicable codes is one way to do that. Besides the international building codes that regulate the design, construction, alteration, and maintenance of new commercial and residential buildings, there are seismic codes. These are provisions that ensure structures can withstand earthquake forces.
Buildings made to withstand earthquakes may not look remarkable from the outside. However, numerous aspects make them more resilient during these disasters. Here are five of them:
1. An Appropriate Foundation
Creating a flexible foundation for a building could help it stay standing during an earthquake. One option is to build the structure on top of pads that separate the building from the ground. Then, the pads move, but the building stays still.
Another similar possibility, described in a 2019 research paper, is to place a solid foundation slab made of reinforced concrete and crisscrossing strips atop an intermediate cushion of sand.
This approach also included a trench around the foundation for further protection. Since this foundation design kept the building’s base away from the soil, it was more resistant to seismic forces.
2. Seismic Dampers
Earthquake-resistant buildings also need features to help absorb shocks. People more commonly refer to them as seismic dampers. Engineers worked with NASA to develop damper systems for swing arms on its rockets in the 1960s. It chose a gas-driven shock isolation system first, then eventually progressed to a fluidics-based system that’s still used today during space station launches and for earthquake-proofing buildings.
Seismic dampers absorb destructive energy, protecting the building from sustaining it. Generally, the larger the damper’s diameter, the more force it can handle. One manufacturer of these dampers sells products to withstand from 25 to 1,100 tons and sells customized options, too.
Another approach involves putting a thin layer of graphene on top of a natural rubber pad. Researchers believe this will be a low-cost damper option for commercial and residential buildings.
3. A Drainage Mechanism
Pooled water can create structural complications. That’s why parking garages often have double-tee load-bearing structures with a twist that lowers one corner — a feature called warping. Engineers achieve positive drainage with 1.5 percent minimum slopes across the diagonal toward floor drains. Drainage is also crucial to help structures tolerate earthquakes.
When the disasters occur in places with loose, sandy soils, the shaking can result in a phenomenon called liquefaction. It makes buildings sink or move to one side, and sewage pipes may rise to the surface. When the soil solidifies again after an earthquake, the buildings stay in their sunken, tilted positions.
However, earthquake drains help collected water escape, preventing liquefaction. They are prefabricated pieces wrapped in a filtering fabric. Each drain measures between 3 and 8 inches in diameter. A successful installation requires a grid-style placement. Depending on the size of the area prone to liquefaction, a building may need hundreds or thousands of drains.
4. Structural Reinforcement
Engineers and designers have various methods for strengthening a building’s structure against potential earthquakes. Many of those redirect seismic forces. For example, shear walls and braced frames transfer lateral forces from the floors and roof to the foundation.
Then, diaphragms are rigid horizontal planes that move lateral forces to vertical-resistant parts of the building, such as a building’s walls or framework. There are also movement-resistant frames. Those possibilities make a building frame’s joints rigid while letting the other parts move.
Shorter buildings have less flexibility than taller ones. Thus, engineers typically realize they must provide more structural reinforcement for structures that are only a few stories tall versus skyscrapers.
5. Material With Adequate Ductility
Ductility describes how well a material can tolerate plastic deformation before it fails. Thus, materials with high ductility can absorb large amounts of energy without breaking. Structural steel is one of the most ductile materials, while brick and concrete are low-ductility materials.
Researchers have also developed creative solutions that show how structural steel is not the only earthquake-resistant material worth considering. For example, scientists engineered a fiber-reinforced concrete with properties similar to steel. They called the material eco-friendly ductile cementitious composite. Experiments showed applying a 10-millimeter-thick layer to interior walls protected them from damage during a 9.0-magnitude simulated quake.
Projects are also underway to build earthquake-resistant residences in nations that lack the resources for safely built houses made from materials that people may need to import or lack the skills to use correctly — such as concrete and bricks. A civil engineering company showed how people in Indonesia could construct earthquake-resistant homes almost entirely from bamboo. The roofs feature corrugated sheets made from recycled Tetra Pak, a lightweight material that reflects heat.
Thoughtful Decisions Can Save Lives
Tens of thousands of earthquakes happen globally every year. Although some cause minor or no damage, others lead to collapsed buildings, loss of life and tremendous disruptions to local economies.
The above list is not all-encompassing, but it includes five things that should come up in every conversation about helping a building resist earthquakes. When architects, construction workers and other professionals protect a structure against seismic activity from the start, they’ll contribute to safer, more sustainable and more productive communities.
Emily Newton is the Editor-in-Chief of Revolutionized Magazine. She has over three years experience writing articles in the industrial sector.