How Do We Make Buildings Survive Earthquakes?Admin
Earthquakes are a devastating natural disaster and can vary in size, with some causing more destruction than others. Earthquakes can be caused by the movement of one of the Earth’s 20 moving tectonic plates, a volcanic eruption or are the effect of a meteor collision.
The scope for creating earthquake-efficient buildings has much range, and there are many parts to their engineering. In this article, we shall give a basic overview of some of the main aspects of these construction designs and how they withstand earthquakes.
Which Buildings Can Withstand an Earthquake?
Unfortunately, we live in a time where it is not possible to construct an entirely safe building that is completely immune to damage caused by an earthquake, before an earthquake has struck.
However, earthquake-resistant construction is engineered with the structure to embrace more substantial ground activity.
How Does Earthquake Resistant Construction Work?
Earthquake resistant construction is produced by taking into account the magnitude of earthquakes local to the area to where it is erected. In America, for example, a National Seismic Hazard Map produced by the U.S. Geological Survey shows the likelihood of where areas are likely to surpass a specific amount over the next half a century.
Using this information, if an earthquake were to hit, the earthquake-resistant building should be able to withstand the shift and not collapse and, in theory, minimise the loss of life in the surrounding area.
Of course, this is not a guarantee, and its capability will only be known when struck by a real earthquake. Until that has happened, it will remain as a prototype.
Considering the Base of the Construction in an Area with Potential Earthquakes
One significant starting point of the building’s construction is to ensure that the foundation of the building is stable. Some ground substances are more substantial and outperform others.
For example, bedrock is known for its sturdiness and tends to be favoured as a substrate.
On the other hand, certain substances such as filled-in and soft soil are weak when planning a building which needs to be able to withstand an earthquake.
When loose substances such as these are used for the foundation of a building, they pose the threat of liquefaction. Liquefaction is when these loose substances act as more of a liquid, rather than a solid, and cause buildings to sink or move on top of them during an earthquake.
Design of the Building
When creating a building to retain strength during an earthquake, torsion needs to be avoided. Torsion is when a structure is twisted during the movement caused by an earthquake, resulting in the tension and subsequent weakening of a material.
Designs which are avoided include:
- Irregular design
- Asymmetrical designs
- Split level structures
- L- shaped buildings
- T- shaped buildings
The Preference of Symmetry
Symmetrically designed buildings are more suitable in resisting earthquakes. The symmetry of a structure allows for more of an even distribution of energy. Designs should be kept simple, with less unnecessary decorative elements which may cause upheaval and therefore ruin.
The Foundations of an Earthquake-Resistant Building
Ideally, the foundations of a more durable building during an earthquake will absorb energy. The term ductility is used concerning this requirement. It relates to how a material can be stretched or impacted with a reduced amount of damage or breakage. Metals tend to be highly ductile because they can be bent without breaking.
Foundation Materials to Avoid
Substances such as brick and concrete are unsuitable for foundations due to their lack of absorption and ductility.
Foundation Materials Often Used
On the other hand, steel-reinforced concrete is a suitable choice. Its reliability comes from the steel, which increases its malleability. A construction produced by steels plates, beams and angles will offer the best solution.
Other Alternate Solutions
Active mass damping is a system engineered that is not only reliant on the durability of the building’s foundation. In a basic description of active mass damping, a weighty mass is installed at the top of the building and acts as a shock absorber through a connection to viscous dampers.
Consequently, the building sways in the alternate side to the initial ground movement. In turn, mechanical vibrations decrease in size.
Innovative Designs for an Earthquake-Resistant Building
There are a number of specific structures which hope to remain resilient in the face of an earthquake. Below we offer a basic summary of a couple of innovations created by engineers.
The aim of the Rocking Frame structure is for residents to return at a faster rate. The structure remove consists of :
- Steel cables
- Steel frames
- Steel fuses
In theory, the steel frames which create the building can freely move vertically up and down. The steel fuses at the base of the building, which are laid out similarly to teeth, absorb the energy causing them to open and close. Even if the fuses do not withstand the earthquake, the steel frame should be unharmed.
After the movement has ended, the steel cables then essentially tug the building straight up. The steel fuses can then be reviewed and replaced where necessary, allowing the structures to continued usage within a small timeframe.
The Seismic Invisibility Cloak
This structure is the idea that the construction could become ‘invisible’ to the power of the surface waves of an earthquake.
Engineers propose to place around 100 concentric plastic rings below the building. Upon the impact of an earthquake, the rings would compress into a bottleneck form. The energy is then released by exit rings on the other side with the aim for the building to remain upright.
Hopefully, we have provided you with a basic introduction into earthquake-resistant construction, as this only the beginning of the engineering process. There are many parts to constructing a building which has the aim of remaining upright during an earthquake. What impressive innovations are you aware of? Why not let us know on our social media channels?
If you currently need a professional surveyor to oversee your construction in the South West, we have building surveyors in Cornwall with a wide range of knowledge and expertise in health and safety, property law, planning applications and building regulations. Please do not hesitate to get in touch for any assistance you require.