• Aayan Kabra

Research question: How can the seismic safety of buildings be improved through retrofitting and upgradation. Seismic Safety evaluates and performs structural-foundation reinforcements that will reduce the risk of earthquake-induced damage to your home.Earthquakes occur when there is a sudden release of energy in the Earth's crust, which creates seismic waves. This energy can be caused by the movement of tectonic plates, volcanic activity, or man-made activities such as the use of explosives or the filling of reservoirs. The point where the energy is released is called the focus, and the point on the Earth's surface directly above the focus is called the epicenter. The magnitude of an earthquake is determined by the amount of energy released and is measured on the Richter scale.Earthquakes happen as a result of tectonic activity, which is caused by the movement and collision of the Earth's crustal plates. The Earth's surface is divided into several large and small tectonic plates, these plates are always moving, but very slowly, due to the convection of the Earth's mantle. When two plates collide or grind past each other, huge amounts of stress and pressure can build up, and when this stress exceeds the strength of the rock, it can cause the rock to break, releasing energy in the form of seismic waves. This energy can also be released by volcanic activity, when magma rises to the surface and causes the ground to move. In addition, man-made activities such as the filling of reservoirs, the use of underground explosives, and even construction activities can also cause earthquakes. The magnitude of an earthquake is measured using the Richter scale, which ranges from 1 to 9. The Richter scale is a logarithmic scale, which means that an earthquake with a magnitude of 7 is 10 times stronger than an earthquake with a magnitude of 6, and 100 times stronger than an earthquake with a magnitude of 5. The Richter scale, also known as the Richter magnitude scale, was developed in the 1930s by Charles F. Richter, a seismologist at the California Institute of Technology. It is a measure of the magnitude, or the amount of energy released, during an earthquake. The Richter scale is a logarithmic scale, which means that each increase in one whole number on the scale represents a tenfold increase in the amplitude of the seismic waves and a thirtyfold increase in the energy released. For example, an earthquake with a magnitude of 6 releases 30 times more energy than an earthquake with a magnitude of 5. The scale ranges from 0 to 9, with 9 being the highest possible magnitude. It is important to note that the Richter scale is only used for earthquakes of less than magnitude 7, for larger earthquakes the Moment magnitude scale is used. The moment magnitude scale is similar to the Richter scale, but it takes into account the total amount of energy released by an earthquake, rather than just the amplitude of the seismic waves. The Richter scale is based on measurements of the amplitude of seismic waves recorded on seismograms. The amplitude of the seismic waves is measured in micrometers (one millionth of a meter) and is then converted to a magnitude value using a formula. The formula used to convert the amplitude of seismic waves into a magnitude value on the Richter scale is: magnitude = log(A) + (Q* log(D)) - 2.8 Where: ● A is the amplitude of the seismic waves measured in micrometers, ● log(A) is the logarithm of the amplitude, ● Q is a correction factor that accounts for the distance between the earthquake's epicenter and the seismometer, ● log(D) is the logarithm of the distance from the epicenter to the seismometer, and ● 2.8 is a constant that is used to adjust the magnitude value to a specific reference distance of 100 km. This formula is based on the assumption that the amplitude of seismic waves decreases with distance from the epicenter. The correction factor Q is used to account for this decrease in amplitude and is typically around 2 for local earthquakes and around 1 for regional and teleseismic earthquakes. It is important to note that the Richter scale is only valid for relatively small earthquakes. For larger earthquakes, the Moment magnitude scale is used, which measures the total amount of energy released during the earthquake. The formula for the moment magnitude scale is based on the seismic moment, which is calculated from the amplitude, frequency, and duration of the seismic waves, and the size of the fault that caused the earthquake. “The taller the building is, the deeper the foundation is” The buildings are usually designed in such a way that they can resist a magnitude of 4.5 of the Richter's scale, as far as residential buildings are concerned. The energies released during an earthquake are Kinetic energy, thermal energy and sound energy. There are several techniques to improve the earthquake resistance of buildings, of course this will increase the builders cost of production, but someone rightly stated, you cannot put a price on life. The first technique is deep foundation technique. The main idea behind this technique is that deep foundations such as piles of caissons, are used to transfer the weight of the building down to deeper, more stable soil or rock layers. This effectively lowers the center of mass of the building. According to the law of physics, for an object to gain more stability, it has to have a lower center of mass or gravity(a point at which most of its mass is concentrated at), or it should increase its base area. A building cannot widen its base area as that would require the builder to acquire more land which would significantly increase the cost of production, so the only other viable way is to lower its center of gravity. This makes the building more stable and allows it to persist through severe waves of energy.This can help to reduce the amount of movement and deformation that the building experiences during an earthquake.On the other hand, if the building's center of mass is already very low, such as a single-story building, the deep foundation may not lower it much more. This can be the case with a building that has a shallow foundation and a low center of mass. In this scenario, using a deep foundation may not provide much additional stability, but it will help to transfer the loads to deeper soil layers. Overall, the goal of the deep foundation technique is to reduce the amount of movement and deformation that the building experiences during an earthquake, rather than necessarily lowering the center of mass. The center of mass is just one of many factors that are considered when designing a building's foundation for seismic resistance. Another technique is to use a base isolation system.Base isolation is a type of seismic retrofitting technique that is used to reduce the amount of seismic energy that is transmitted to a building. The goal of base isolation is to reduce the amount of structural damage and to improve the safety of the building during an earthquake.This involves placing a layer of material, such as rubber or lead, between the building's foundation and the ground. The material is designed to be flexible and compressible, so that it can absorb some of the energy of the seismic waves and reduce the amount of movement that the building experiences. As we know from the law of conservation of energy, energy can neither be created nor destroyed, it can only be transformed from one form to another.In a base isolation system, rubber or lead is used as a layer of material between the building's foundation and the ground. The material is designed to be flexible and compressible, so that it can absorb some of the energy of the seismic waves and reduce the amount of movement that the building experiences.The rubber or lead isolation layer works by dissipating the energy of the seismic waves through a combination of deformation and damping. The rubber or lead will compress and stretch under the force of the seismic waves, effectively reducing the amplitude of the waves and the amount of movement that is transmitted to the building. This is similar to how shock absorbers in a car work, they absorb the energy from bumps in the road by compressing and then releasing that energy slowly.The rubber or lead isolation layer also has damping properties, which means that it is able to dissipate some of the energy of the seismic waves as heat. This helps to further reduce the amount of movement that is transmitted to the building.It is important to note that base isolation systems are not a substitute for good seismic design and construction practices, but rather an additional measure to reduce the seismic risk for a building. The design and the material of the isolation layer will vary depending on the seismic hazard of the location, the type of building, and other factors. Base isolation systems are typically composed of a series of isolation bearings, which are placed between the building's foundation and the ground. The isolation bearings can be made of different materials, such as rubber, lead, steel, or a combination of materials. The isolation bearings are designed to be flexible and to compress or rotate under the force of seismic waves, effectively reducing the amplitude of the waves and the amount of movement that is transmitted to the building. There are several different types of base isolation systems, including: ● Elastomeric bearings: These are made of rubber or a rubber-like material and are designed to compress and stretch under the force of seismic waves. ● Lead-rubber bearings: These are made of a combination of lead and rubber and are designed to compress and rotate under the force of seismic waves. ● Friction pendulum bearings: These are made of steel and are designed to rotate under the force of seismic waves. Rubber's ability to absorb energy as a base isolation material is due to its unique structural properties. Rubber is a viscoelastic material, which means that it exhibits both viscous (fluid-like) and elastic (solid-like) behavior when it is deformed. This allows rubber to absorb energy by deforming under load, and then returning to its original shape when the load is removed. When an earthquake occurs, the ground shakes and generates seismic waves that can cause a building to move. The movement of the building is transmitted to the foundation, and then to the isolation bearings. The rubber isolation bearings compress and stretch under the force of the seismic waves, effectively reducing the amplitude of the waves and the amount of movement that is transmitted to the building. This process is known as energy dissipation. Rubber's ability to absorb energy also depends on the design and the quality of the rubber isolation bearings. The isolation bearings are typically composed of several layers of rubber, each with different properties. The outer layer is usually made of a harder rubber that is designed to protect the isolation bearing from damage, while the inner layer is made of a softer rubber that is designed to absorb energy. The thickness and the properties of the rubber layers can be adjusted to optimize the isolation bearing's energy dissipation capabilities. It's worth noting that rubber is not the only material used in base isolation systems, lead rubber bearings are also used and they have different properties than pure rubber, they have a higher energy dissipation capacity and also can be used in higher seismic hazard zones. In some cases, the base isolation system can reduce the damage caused by about 90%, qualifying it to be an effective measure at increasing the seismic safety of buildings by retrofitting. Last but not least, another way to reduce the impact and aftereffects of earthquakes is seismic raft foundation.A seismic raft foundation is a type of foundation system used to provide stability and support for buildings and structures in areas prone to earthquakes. It is a type of mat foundation, which is a large concrete slab that covers the entire footprint of a building. The slab is designed to spread the load of the building evenly across the soil and to provide a flexible, stable base that can move with the ground during an earthquake. The raft foundation is reinforced with steel rebar to increase its strength and ductility, and it may also include additional features such as seismic isolation bearings to further reduce the impact of earthquakes on the building. Seismic isolation bearings are often incorporated into the design of the raft foundation to further reduce the impact of earthquakes on the building. These bearings are located between the foundation and the building and are designed to be able to move in any direction, allowing the building to move independently of the foundation during an earthquake. This helps to reduce the amount of stress and strain on the building, as well as the amount of energy that is transferred from the seismic waves to the building. Seismic raft foundation is a modern and advanced foundation system that is designed to provide stability and support for buildings and structures in areas prone to earthquakes. It is a type of mat foundation, which is a large concrete slab that covers the entire footprint of a building. The slab is typically between 1 to 1.5 meters thick and is reinforced with steel rebar to increase its strength and ductility. The raft foundation is designed to spread the load of the building evenly across the soil, providing a stable and flexible base that can move with the ground during an earthquake. The design of the seismic raft foundation takes into account the soil conditions, the expected magnitude and frequency of earthquakes, and the load-bearing capacity of the foundation. The foundation must be able to support the weight of the building and the forces generated by seismic waves, while also providing enough flexibility to prevent damage to the building during an earthquake.Seismic isolation bearings are often incorporated into the design of the raft foundation to further reduce the impact of earthquakes on the building. These bearings are located between the foundation and the building and are designed to be able to move in any direction, allowing the building to move independently of the foundation during an earthquake. This helps to reduce the amount of stress and strain on the building, as well as the amount of energy that is transferred from the seismic waves to the building.In summary, Seismic raft foundation is a modern and advanced foundation system that is designed to provide stability and support for buildings and structures in areas prone to earthquakes. It is a type of mat foundation which is a large concrete slab, reinforced with steel rebar that is designed to spread the load of the building evenly across the soil, providing a stable and flexible base that can move with the ground during an earthquake. It may include seismic isolation bearings to reduce the impact of earthquakes on the building. CITATIONS AND REFERENCES: ● Image of the Righter scale graph-https://joans-place.com/pluginfile.php/1266/mod_imscp/content/1/m30_1_m6/m6/ m30_1_m6_l03_exp_p06.html ● Formula to calculate magnitude of earthquake from amplitude of seismic waves:Book "Seismology and Plate Tectonics" by W. Kenneth Hamblin ● “The taller the building is, the deeper the foundation is”- Splittingram

"How can the seismic safety of buildings be improved through retrofitting and upgradation.", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.10, Issue 1, page no.f27-f30, January-2023, Available :http://www.jetir.org/papers/JETIR2301504.pdf

"How can the seismic safety of buildings be improved through retrofitting and upgradation.", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.10, Issue 1, page no. ppf27-f30, January-2023, Available at : http://www.jetir.org/papers/JETIR2301504.pdf