Top-to-toe toughness Buildings are designed to resist earthquakes in a variety of methods, including modifications to the building's foundation. However, motion dampers installed throughout the building's height can increase resilience. This method has the potential to minimize vibrations within the structure.
Seismic strengthening A building can be made stronger by using materials that resist damage from an earthquake, such as reinforced concrete or steel. In addition, structural reinforcements can be added to existing buildings to make them more resilient. For example, door and window frames may be strengthened by using metal braces to prevent breaking under stress. Walls may also be strengthened by using internal bracing to prevent collapse.
Tectonic plates Earth's surface is made up of many different types of material including continents, oceans, and rocks. Between these layers is a thick layer of liquid water called "the mantle." Beneath the mantle lies Earth's core, a solid sphere of iron and silicon atoms. The outer part of the core is mostly solid oxygen, with some nitrogen and traces of other elements. All this is wrapped in a thin layer of molten rock, which extends down into Earth's deepest parts.
The movement of tectonic plates creates the major mountain ranges and deep trenches on Earth's surface. It also causes frequent earthquakes and changes to Earth's crust, resulting in volcanoes erupting everywhere from Africa to Antarctica.
Seismic vibrations wreak havoc on poorly constructed structures. These locations will be safer to live in if structures are appropriately engineered and built to resist these vibrations. A seismic safe design aims to reduce the impact of an earthquake on buildings by considering how they are built down to the smallest detail. The goal is to create a structure that is as immune to earthquakes as possible.
There are two types of seismic safety: structural and non-structural. Non-structural elements include furniture, appliances, and other personal property. They can be damaged or destroyed during an earthquake, so it is important to identify them in a home inspection and note their location in your report. Structural elements include walls, floors, and roofs. They must be considered when designing a house or building site, since their damage could affect the stability of the entire structure.
The American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) has published a comprehensive set of guidelines for seismic safety in buildings. Their guideline documents are useful tools for identifying risk areas in homes and recommending solutions that will make buildings more resistant to earthquakes.
Structures are made up of components that move independently from one another. When an earthquake strikes, these components need to know what type of movement to expect so they can protect themselves.
Devices such as isolation systems and dampers, which are meant to limit vibrations (and hence damage) caused by earthquakes, are effectively used in the construction of new buildings. The most common devices are isolators and dampers. Isolators are mechanical breakers that shut off power to an entire section of wall-mounted equipment when they detect a heavy vibration, which indicates that further equipment inside the room is still functioning properly. Dampers are similar to isolators in function but use liquid instead of springs to cut off power. They can be installed between power outlets on a circuit board or plugged into a separate receptacle if there is no outlet nearby. Both types of device are very effective in preventing costly damage to ungrounded electrical appliances such as hair dryers, vacuum cleaners, and air compressors.
Other devices include surge protectors and voltage stabilizers. A surge protector uses a capacitor or zener diode to absorb energy from an incoming voltage waveform and dissipate it as heat. This prevents damaged equipment due to high currents generated during a lightning strike or other large transient voltages. Voltage stabilizers operate by using a resistor to divide up the voltage from the mains supply so that only a small portion of it reaches the appliance being used at any given time. This ensures that nothing will work when the power comes back on after an interruption.
Dampers, it turns out, can be advantageous for constructing earthquake-resistant structures. Dampers are often installed on each floor of a structure, with one end attached to a column and the other end attached to a beam. Each damper is made up of a piston head that rotates inside a silicone oil-filled cylinder. As the building experiences an earthquake, the piston head moves inside the cylinder, which opens and closes the valves on the outside of the cylinder tube.
The seismic design requirements for buildings that use dampers as part of their resistance against motion caused by earthquakes are different from those for traditional buildings. Traditional buildings tend to suffer more damage during an earthquake because they rely primarily on friction between their various construction elements (such as wood) to prevent movement. However, seismic buildings tend to rely more on gravity to keep them in place during an earthquake because frictional forces are not enough to overcome gravitational force. This means that they need to be designed with greater depth than would otherwise be required if friction alone were used as a resisting force.
In addition to being deeper, seismic buildings must also be stronger both within and below the surface of the ground. The studs that make up the frame of the building should be thicker and spaced farther apart than those in traditional buildings. The foundation of the building needs to be strong enough to resist any pressure that might be applied it by an earthquake, so it usually consists of deep holes dug into the earth and filled with concrete or steel.