Earthquake Resistant Construction Standards
Often times when an Earthquake strikes, the main event is followed by a number of smaller but equally significant tremors called aftershocks. While the aftershocks may be less severe than the main earthquake in terms of its intensity, it is as likely to cause death and damage as the main earthquake. This is because the core foundations of the buildings are damaged by the earthquake and when this is followed by aftershocks, they become the reason for the buildings to collapse.
Earthquake Engineering is the science of construction of buildings that not only provide resilience to the structure in the event of an earthquake but also ensure that the structure remains operable for the rescue period following the earthquake when there are aftershocks. When we say "remains operable", it also refers to the layout of the building that ensures the movement of rescue personnel and their equipment during the rescue efforts without major hindrance.
Important Earthquake Engineering Concepts
Seismic Frequency Dissipation: Do you know that a band of marching soldiers are always asked to stop marching along when crossing a bridge? This is because when soldiers march along on a bridge, the frequency of vibration caused by each of the soldiers adds up to what is called the harmonic frequency which can cause swaying of the bridge - something that can be deadly at times.
When a building is constructed, it should be ensured that the structure is not in such a way that the vibration caused by the movement of one portion of the building is in sync with the vibrations from the other parts of the building. This, like in the example above, can worsen the already swaying construction. The set of controls used to achieve this are called seismic vibration controls.
Base Isolation and Damping: One way to prevent vibration from the seismic waves from causing havoc to the building structure is by deploying lead rubber bearing that isolates the base of the building from the rest of the structure. The elastic nature of the material often absorbs the shock waves sent from the bottom of the building by the tremors. This dampens the overall seismic effect from the base of the building towards the rest of the structure.
Pyramidal Structures: Wonder why a lot of massive skyscrapers are shaped with a broad base and a pointed peak? Well, it is based on the science that pyramidal structures are more resistant to seismic waves than any other. Such structuring ensures that the center of gravity of the building stays inside the area covered by the base thereby making the building pretty resistant to tremors.
There are various other construction standards that are put forward by earthquake engineering scientists and most of them are focused on dampening the vibrations arising from the bottom of the building structure and distributing the stress caused by the vibrations evenly across the system so that the structure does not collapse. However, most of the new learnings continue to come from structures that collapse during an earthquake. Studying the building designs along with the failure points help scientists gauge the success or failure of their proposed standards that help in a continual improvement process towards ensuring quake-resistant constructions in the future.