Structures are often intended to sustain vertical loads, therefore vertical shaking caused by earthquakes (which either adds or subtracts vertical loads) is addressed by safety considerations incorporated into the design to support vertical loads. For example, building codes require that structures be designed to with stand the load of any remaining furniture and other contents after an earthquake.
When a strong earthquake strikes, buildings experience sudden changes in weight, pressure, and tension. Unless the structure is designed to accommodate these changes, it may suffer damage that could be prevented if it were made stronger or more resistant to begin with.
The three main types of failure modes for buildings are collapse, sag, and release of stored energy. After an earthquake, structural systems must be able to resist all major forces acting on the building. This includes maintaining its original height, with no sags or dips in the flooring. Any loss of strength or rigidity of construction materials or system components can lead to failure to maintain adequate resistance to loading conditions. An example would be breaking windows in an attempt to create a draft to remove excess heat from the room, which would reduce the stress on the structure.
Seismic design involves considering how earthquakes might affect a building. It focuses on determining what forces will act on the building and how those forces might cause the building to fail.
Structural tensile stress The primary way an earthquake impacts structures is through ground shaking. Inertial forces are created in the structure by the fast acceleration of the earth beneath the building. This might cause harm if they become too large or if the building is not built to handle them. Ground shaking can also cause objects such as rocks, bricks, and dust to fly up into the air. These falling objects can be dangerous to people because they can hit them on the head or neck.
Other ways in which earthquakes impact structures include: Falling objects such as bricks, glass, and wood that are located outside of buildings can cause injuries to people who happen to walk through them. An example would be if a window breaks during an earthquake and brick falls onto a person's head. Tiles that are used in flooring can be damaged by heavy equipment moving around warehouses during recovery efforts after an earthquake. If you work in an industry related to construction, like engineering or law enforcement, you need to know how earthquakes may affect your job.
You will be able to feel the ground moving under your feet and objects being thrown about during an earthquake. Strong vibrations will spread through the ground as far as 10 miles from the epicenter. These vibrations can damage buildings, but only if the intensity is high enough. After a major earthquake, further damaging vibrations may occur as blocks move underground.
The principal source of earthquake damage to man-made structures is ground shaking. Many factors determine the severity of earthquake shaking at a location, including the magnitude of the earthquake, the location's closeness to the fault, local geology, and soil type. But one factor that affects everyone is distance from the epicenter. The closer you are to the epicenter, the more severe will be the shaking. Seismic waves propagate at the same speed in all solid objects, so any building will suffer damage if it isn't strong enough to resist being shaken by the wavefronts.
Earthquakes can also cause damage through their effect on human behavior. For example, people may run out of buildings or into open spaces in panic, causing additional injuries or death. Damage to infrastructure, such as roads and bridges, can also result from earthquakes. Finally, earthquakes can trigger secondary disasters, such as flooding or mudslides caused by fallen trees and debris.
Human activity has had a significant impact on the frequency and intensity of earthquakes. Humans have been altering the Earth's surface since they first started farming thousands of years ago, so it isn't surprising that many areas experience earthquakes now and again. Human activities include changing the landscape through deforestation and urban development, which removes soil support and can lead to landslides; clearing land for agriculture; and even nuclear testing.