Beautiful cities and constructions have been built by mankind throughout history, only for them to be destroyed by natural forces. The mere mention of earthquakes, which are classified as natural disasters, does not give off a very positive impression. Earthquakes are one of the planet’s most destructive forces; seismic waves that travel through the ground have the power to damage structures, claim lives, cause enormous financial losses, and more.
The National Earthquake Information Center estimates that there are typically 20,000 earthquakes each year, 16 of which are major disasters. Similar to earthquakes, most damage is brought on by buildings collapsing while occupants are still inside, necessitating the construction of earthquake-proof structures.
However, in older eras, when the type of structures was usually closer to the ground and did not reach a very significant height, there would be opportunity to run to an open area for minimal harm. But given the current situation, where high-rise structures are crammed closely together, there is little choice but to design the structures so that they can survive seismic activity. Engineers have improved building earthquake resistance over the past few decades by introducing new building designs and materials. These kinds of buildings are referred to be earthquake-resistant structures.
Earthquake-resistant structures are those built to resist total collapse, protect life, and reduce damage in the event of an earthquake or tremor. Through a variety of techniques, earthquake-resistant structures absorb and dissipate seismically produced motion: damping reduces the amplitude of oscillations of a vibrating structure, and ductile materials (such as steel) can endure significant inelastic deformation.
The article will describe the various approaches to earthquake-proof building design.
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Understanding Earthquake – Resistant Structures
Buildings are intended to be protected from earthquakes to some extent or completely by earthquake-resistant or aseismic construction. The aim of earthquake engineering is to build structures that perform better during seismic activity than their conventional counterparts, even though no construction can be completely resistant to earthquake damage. Building regulations state that earthquake-resistant constructions must be able to withstand the biggest earthquake with a specific probability that is expected to strike the area where they are located. This means that in the event of a rare earthquake, the death toll should be kept to a minimum by preventing building collapse, while in the event of a more regular earthquake, the functional loss should be kept to a minimum.
From the outside, buildings designed to resist earthquakes may not stand out. They are more resilient during these disasters, nevertheless, due to a number of factors.
How to Make a Building Earthquake-Proof
When experts plan and develop structures, they consider ways to lower dangers. Engineers labour to strengthen the structure and mitigate the effects of a prospective earthquake when creating an earthquake-proof building. Buildings are pushed in one direction by an earthquake’s discharge of energy; the approach entails having the building push in the opposite direction. These safeguards make sure that buildings can survive the effects of earthquakes. Here are a few techniques for making structures more earthquake-resistant.
Base isolation is a technique used to “raise” the building’s foundation above the ground in order to withstand ground stresses. Base isolation entails erecting a structure on top of flexible steel, rubber, and lead pads. The isolators vibrate when the base shakes during an earthquake, but the building itself doesn’t move. As a result, seismic vibrations are successfully absorbed and kept from passing through the building.
Buildings that can withstand earthquakes must also include characteristics that can absorb shock. They are more frequently referred to as earthquake dampers by engineers. The shock absorbers used in automobiles are comparable to seismic dampers. Shock absorbers work similarly to how they do in automobiles i.e. they lessen the force of the shockwaves and lessen the strain on the structure. Pendulum power and vibrational control devices are used to achieve this.
The dampers are positioned between columns and beams on each level of a building. Each damper comprises of a cylinder containing silicone oil and piston heads. When there is an earthquake, the structure’s vibrational energy is transferred to the pistons, which press on the oil. The force of the vibrations is then dissipated as a result of the energy’s transformation into heat. By absorbing damaging energy, seismic dampers prevent the building from being damaged. Generally speaking, the damper can withstand higher stress the larger its diameter.
Earthquake-Proof Structural Reinforcement
Different techniques are used by engineers and architects to fortify a building’s framework against potential earthquakes. Buildings must redistribute the seismic forces that pass through them in order to withstand collapse. For instance, the main components of a building’s reinforcement include shear walls, cross braces, diaphragms, and moment-resisting frames.
These wide beams, which are given for high strength and stiffness, are vertically orientated. While core walls are made up of channel sections that are best used without any gaps, these are either plane or flanged in section. In high rise buildings, their thickness typically ranges from 150 mm to 400 mm. These walls ought to have symmetrical plans on both axes.
Another essential component of a building’s structure is its diaphragm, which transfers lateral stresses to the structure’s vertically resistant walls or framework. Diaphragms, which are made up of the building’s floors, roof, and decks atop them, assist in pushing forces to the building’s vertical supports and relieving floor strain. There are also frames that can withstand movement.
Buildings are shaken from left to right by s-waves during an earthquake, therefore bracing keeps the shape and prevents the structure from becoming weaker. Different types of bracing, such as diagonal bracing, x-bracing, v-bracing, inverted v-bracing, and k-bracing, can be utilised. When diagonal supports in a building structure intersect, cross bracing is used to strengthen the structure.
Shock absorbers, pendulums, and “invisibility cloaks” could, to some extent, assist in dispelling the energy, but the materials choose for a building are also in charge of its stability. High ductility materials can therefore take in a lot of energy without breaking. Brick and concrete are low-ductility materials, although structural steel is one of them. Structural steel, which comes in a variety of shapes and allows buildings to bend without breaking, is frequently used in the construction of modern buildings. Due to its considerable strength in comparison to its lightweight structure, wood is also an unexpectedly ductile material.
Each year, there are thousands of earthquakes worldwide. While some only cause slight or no harm, others result in building collapses, fatalities, and severe economic disruptions in the area. Because careful choices can save millions of lives every year, it is important to allow for some structural damage, resist lateral loads with stiffeners (diagonal sway bracing), and for different parts of the building to move independently.