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India is prone to earthquakes due to its location on two major tectonic plates. Over the years, earthquakes have destroyed many homes and lives lost. Hence, it is crucial to follow strict construction standards and protocols when building a home in an earthquake-prone region in India. Proper planning and use of earthquake-resistant techniques can help minimize damage to your home during an earthquake.
India follows the National Building Code (NBC) to enhance the structural safety of buildings in earthquake-prone regions. Key aspects include:
India is divided into four seismic zones (II, III, IV, V) to determine appropriate construction techniques based on seismic activity.
Building designs must conform to the standards applicable to their seismic zone, ensuring that proper materials and alignments are used.
Adopting ductile materials like steel and reinforced cement concrete (RCC) for improved earthquake resistance.
Ensure strict control of materials and construction processes, and conduct regular inspections.
Select foundations based on seismic zones, with isolated or raft foundations recommended for high seismic activity areas.
Strengthening existing structures to improve earthquake resistance.
Following these construction standards can mitigate damages and save lives during earthquakes.
During an earthquake, the ground shakes in different directions, causing the foundation of a building to shake as well. Since the foundation is connected to the ground, this shaking spreads throughout the building. As a result, the building may wobble from side to side because of the horizontal shaking. The floors of the building can also move differently, which puts stress on the vertical parts like walls and columns. This stress can make building materials crack or break, which can seriously harm the building's strength. In the worst cases, if the shaking is very strong, the whole building can collapse.
Here are some important earthquake-resistant construction standards that must be followed:
An effective earthquake engineering strategy is isolating the foundation from the ground using base isolators. These base isolators act like shock absorbers between the building and the ground. They are made from layers of rubber and steel and placed under the building's foundation. When the ground shakes, the isolators absorb the earthquake energy and dampen its transfer to the building. This protects the structure from destructive ground motions.
Some types of base isolators used are:
Made of layers of steel plates and rubber bonded together with lead cores. The lead allows the bearings to yield slowly without losing strength.
Consists of an articulated slider between the building base and the ground. The friction absorbs earthquake energy as the slider moves.
Have alternating rubber and steel tightly bonded layers. The rubber layers help flex and dampen vibrations.
These use soft rubber that effectively absorbs seismic energy.
Installing dampers or shock absorbers in the floors and walls creates a counterforce against horizontal shaking. As dampers absorb the vibrational energy and convert it into heat, it reduces the impact on the home. Hydraulic pendulum systems can also be installed to stabilise the structure for construction standards. Some types of seismic dampers used are:
These have metal plates that yield through plastic deformation to dissipate energy.
Use polymers that deform and return slowly to dampen forces.
Use friction between sliding surfaces to dissipate energy.
They have a mass attached via springs or hydraulics that vibrates out of phase with the structure.
Liquid containers tuned to slosh at building frequencies to dissipate energy.
Computer-controlled hydraulic systems that predict and counteract seismic motions.
Seismic vibration control devices can shield the home from damage. This involves creating concentric rings of plastic and concrete around the foundation to reroute the earthquake energy around the home into the ground. This cloak consists of underground concentric rings of plastic and concrete with specific dimensions tuned to the anticipated earthquake vibrations. The key principles are
1. Rings spaced close enough to interact with incoming seismic wavelengths.
2. The speed of seismic waves decreases from inner to outer rings.
3. This causes waves to be directed away from the centre building foundation.
4. Waves take the path of least resistance and flow around the foundation.
5. Buildings don't vibrate in tune with ground motion.
The building structure should be designed to withstand seismic forces and divert them along an intentional load path to the ground. This is done by reinforcing critical structural elements and improving ductility using the following:
Vertical wall elements are designed to resist horizontal seismic forces parallel to the plane of the wall. They add stiffness and act as bracing.
Diagonal structural bracing between beams and columns using steel to reinforce against lateral loads.
Beam-column joints with high rigidity that substantially reduce building sway.
Horizontal elements like floors connecting vertical, lateral force-resisting elements.
Tie all walls/frames together and distribute forces between them.
Provide continuous linkage around walls and frames against discontinuity.
Along with earthquake-resistant design, the choice of construction standards materials also plays a key role:
Steel has high tensile strength and flexibility to endure seismic pressures and vibrations. The right steel reinforcements and frames lend flexibility along with strength. Steel is one of the most suitable materials for earthquake-resistant construction standards in India. It has excellent ductility and malleability to deform reversibly without breaking. The elastic nature enables it to resume its original shape after stress.
The key advantages of using steel are:
1. A high strength-to-weight ratio allows for building lighter earthquake-resistant structures.
2. Strain hardening property increases steel strength as it deforms, which is ideal for energy absorption.
3. Uniform and standardised production enables quality control of material properties.
4. Corrosion resistance through coatings enhances durability.
Wood is lightweight yet has excellent flexibility due to its natural elasticity. This gives it an advantage during earthquakes. Products like cross-laminated timber and plywood can be used per code for floor and roof construction.
Advantages of building with wood:
1. Low density imparts less seismic force on buildings.
2. Light frame wood buildings are flexible to dissipate quake energy through motion.
3. Panels like plywood sheathing provide shear resistance to walls.
4. Wooden shear walls with metal fasteners provide good lateral load resistance.
5. Nailing wooden members together creates dissipative connections.
Special alloys, composites, and polymers like fibre-reinforced plastic and graphene-based materials are engineered explicitly for earthquake resistance. Bamboo is also emerging as an eco-friendly option.
Innovative advanced materials are being developed to enhance earthquake-resistant properties:
This material can return to a pre-deformed shape after strain.
High-strength fibre composites that are lightweight and corrosion-resistant.
Ultra-ductile concrete that can deform without cracking.
Extremely strong carbon nanomaterial is suitable for construction standards.
In conclusion, creating earthquake-resistant homes in India is achievable through smart structural design and appropriate materials and also by paying mindful attention to building specifications and construction protocols. Some crucial methods include flexible foundations, reinforcement construction, damping systems, reinforced concrete walls and frames, shear walls, and the use of materials like steel, wood, and engineered composites. These measures employed due to construction standards ensure that buildings can withstand powerful earthquakes, safeguarding human lives and property.
