Seismic Strengthening For Buildings

In areas of the world prone to earthquakes, there are strict rules that buildings must adhere to. These are designed to ensure that the structure will withstand an earthquake without the loss of life or serious damage to its occupants. The most important aspect of seismic strengthening for buildings is the design and construction methods used for a building’s support structures, foundation, connection joints and structural members.

Buildings need to be strong enough to hold their own weight, but also have flexibility to flex with the ground movement of an earthquake. Structural engineers use a wide variety of methods to increase a building’s strength and flexibility. One method is to increase the amount of rebar in its concrete, which helps it resist shear forces, which are the most destructive force that an earthquake can create. Another way is to strengthen the connections between support elements, such as beams and columns. This is accomplished by adding a brace that runs diagonally from the center of a column to its outside corner, and from a cross member to its opposite side. This method is called a moment-resisting frame.

Engineers also try to make a building more flexible by using materials with a high strength-to-weight ratio, like steel and reinforced concrete. This allows them to bend and flex more readily during an earthquake, reducing the force that it takes for a building to collapse. In addition, they use special connections, such as those that join beams and columns to their foundations or other supports, to reduce the likelihood of structural failure in an earthquake.

Some earthquake-resistant designs take advantage of the fact that an earthquake’s forces travel in waves, which means that they are stronger at the bottom of a building than they are at the top. This is why buildings in seismic zones often have their base isolated from the rest of the building. These systems, which are sometimes referred to as “base isolators,” can come in a number of forms. Some are large, rubber-like plates that squish when the ground moves atop them, absorbing some of the force. Others are more sophisticated, such as a set of two parallel plates made frictionless so that they can slide past each other when the earth lurches beneath them.

Newer techniques focus on ways to deflect and reroute the energy of an earthquake. For example, researchers are working on an eco-friendly coating that can be applied to interior walls of buildings that makes them more resistant to horizontal stress from an earthquake. Alternatively, engineers can try to reroute the energy by burying a series of 100 concentric plastic and concrete rings at least 3 feet underground. As seismic waves enter these rings, they are channeled through the innermost ring and dissipated into the ground, leaving the building largely unharmed by the earthquake. This is a technique that could be particularly effective for homes with living spaces over the garage, which are often not retrofitted to withstand an earthquake.