How do engineers design earthquake-proof buildings?
In: Engineering
**Understanding Earthquakes**
Engineers must understand an earthquake’s impact and the materials and structural devices needed to counteract its impact when designing earthquake-resistant buildings. According to[ FEMA](https://training.fema.gov/emiweb/is/is8a/is8a-unit4.pdf), the Federal Emergency Management Agency, “All objects have a ‘natural period,’ or the time it takes to swing back and forth.” Seismic waves move the ground at its natural period. If the period of the ground is the same as the period of the building, the building can resonate. Resonance causes vibrations to be amplified and places stress on the building.
**Building Materials**
Stress applied to the building is one common cause of building failure, along with improper material use. Engineers must consider how structural materials behave during an earthquake. According to Encyclopedia[ Britannica](https://www.britannica.com/technology/earthquake-resistant-construction), the material property, ductility, is crucial to earthquake resistance. Ductility is the ability of a building to deform without collapsing. One way engineers implement this material property is by reenforcing brittle concrete with steel.
**Tuned Mass Damper**
As well as the consideration of building materials, the use of devices and techniques reduces the horizontal motion of earthquake forces. One example is a device called a tuned mass damper (TMD). A TMD is an inefficient oscillator ([Purdue](https://engineering.purdue.edu/~ce573/Documents/Intro%20to%20Structural%20Motion%20Control_Chapter4.pdf)). The oscillator may be a pendulum or a spring system. An undamped oscillator continues to swing for a long time. So TMDs always have a damper to remove energy in the form of heat like a brake.
**📷**[**Gif Link**](https://www.jssi.or.jp/english/si/img/comparison.gif)
**Base Isolators**
Similarly, a technique called seismic isolation is used to counteract earthquake effects. Seismic isolation separates a building from the ground using stiff pads made of rubber and lead ([ScienceLearn.org](https://www.sciencelearn.org.nz/resources/1022-base-iso)). During an earthquake, the structure’s internal “force is determined by the percentage of the building mass or weight that shakes as a result,” according to [Earthquake-Resistant Structures](https://ebookcentral.proquest.com/lib/calpoly/reader.action?docID=1157391) by Dr. Khan, Mohiuddin Ali. To prevent the structure from shaking with the ground, the base isolator flexes while a seismic damper (lead shock absorber similar to a car damper) absorbs energy as the structure moves.
To design earthquake-resistant buildings, engineers must understand an earthquake’s effect on structures, use proper building materials to avoid building failure, and include devices within the structure that oppose earthquake forces.
Here’s a video for further explanation: [**Video Link**](https://youtu.be/qQcbw7Y6OsU)
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