Earthquakes have always been a terrifying natural phenomenon and it becomes more dangerous as the growing cities come with the risks of collapsing tall buildings.
Why do buildings collapse during earthquakes and how to prevent this?
If you’ve ever watched disaster movies, you might think that buildings collapse as a direct result of the ground beneath them shaking violently or even falling apart. But that’s not really how they collapse because most buildings aren’t in the correct fault position and tectonic plate shifts occur much deeper than the foundations of the buildings. In fact, the effect of earthquakes on buildings is much more complicated.
In fact, the effect of earthquakes on buildings is much more complicated.
So what is the real cause of buildings collapsing?
As the ground moves beneath the building, they send shock waves through the rest of the structure and cause it to shake back and forth. The strength of this oscillation depends on 2 main factors: the mass of the building (mainly concentrated in the roof) and its robustness (the main factor of the oscillation). Low buildings are usually sturdier, while tall buildings are more flexible.
So people think that the anti-collapse solution is to build buildings lower so that they deform as little as possible.
But the 1985 earthquake in Mexico is a good example of that is not entirely true. During the earthquake, many buildings from 6 to 15 floors collapsed. The strange thing is that nearby buildings less than 6 floors are still standing and buildings higher than 15 floors are also mostly unaffected, while mid-sized buildings shake more violently and collapse.
What happened in Mexico was an effect called resonance, where the frequency of the earthquake wave coincides with the natural frequency of mid-range buildings. Like the impulse to the beat for the swing. Each seismic wave will further amplify the shaking of the building and get stronger and stronger eventually going beyond the limits that the building can withstand causing collapse.
Low frequency oscillations will cause much damage to tall and flexible buildings.
Today, engineers work with geologists and seismologists to predict the frequency of earthquakes at construction sites to prevent resonant collapse, based on factors such as soil type or soil type. data from previous earthquakes. Low frequency oscillation will cause more damage to taller and more flexible buildings while high frequency oscillation will be dangerous to low and sturdy structures.
Engineers have also devised a way to absorb vibrations to limit distortion using new technology.