Important Facts to make an Earthquake Proof Building
India comes under High Seismic Zone as per the National Centre of Seismology (NCS). Indian plate is driving to Asia about a rate of 45 mm/year and rotating slowly anticlockwise. As a result, about 56% of India’s land area is prone to medium to severe earthquakes.
India witnessed quite a few devastating earthquakes in recent past which are given below.
|September 30, 1993||Latur|
|January 26, 2001||Gujarat|
|December 26, 2004||Indian Ocean|
|October 8, 2005||Kashmir|
According to building codes, earthquake-resistant structures are intended to withstand the largest earthquake of a certain probability that is likely to occur at their location. This means the loss of life should be minimized by preventing the collapse of the buildings for rare earthquakes while the loss of the functionality should be limited for more frequent ones.
Currently, there are several design philosophies in earthquake engineering, making use of experimental results, computer simulations and observations from past earthquakes to offer the required performance for the seismic threat at the site of interest. These range from appropriately sizing the structure to be strong and ductile enough to survive the shaking with an acceptable damage, to equipping it with base isolation or using structural vibration control technologies to minimize any forces and deformations.
Few important aspects that make your building earthquake-proof are given below:
Design of the Building
Design of the building plays a vital role to make it earthquake resistant. It needs to be perfectly balanced that can be assured by the expert Structural Consultants. Among the most important advanced techniques of earthquake resistant design and construction are:
- Base Isolation Method
- Energy Dissipation Devices
Base Isolation Method
A base isolated structure is supported by a series of bearing pads which are placed between the building and the building’s foundation. A variety of different types of base isolation bearing pads have now been developed. The bearing is very stiff and strong in the vertical direction, but flexible in the horizontal direction. Experiments and observations of base-isolated buildings in earthquakes show that it reduced building accelerations to as little as 1/4 of the acceleration of comparable fixed-base buildings. The base-isolated building itself escapes the deformation and damage, which implies that the inertial forces acting on the base-isolated building have been reduced.
Energy Dissipation Devices
The second of the major new techniques for improving the earthquake resistance of buildings rely upon damping and energy dissipation. As we’ve said, a certain amount of vibration energy is transferred to the building by earthquake ground motion. Buildings themselves do possess an inherent ability to dissipate, or damp, this energy. However, the capacity of buildings to dissipate energy before they begin to suffer deformation and damage is quite limited.
The building will dissipate energy either by undergoing large-scale movement or sustaining increased internal strains in elements such as the building’s columns and beams. By equipping a building with additional devices which have high damping capacity, we can greatly decrease the seismic energy entering the building, and thus decrease building damage. Accordingly, a wide range of energy dissipation devices have been developed and are now being installed in real buildings. Energy dissipation devices are also often called damping devices.
Ductility detailing of Building Structures
Ductility for earthquake resistant design is important for buildings, structures, and building materials. Ductility in general gains a definition in material engineering science as the ratio of ultimate strain to yield strain of the material. In a broader view, ductility is the ability of a structure to undergo larger deformations without collapsing. As per special provisions recommended in codes, the detailing of the structure that lets the structure to gain a larger ductility other than the contributions of material ductility are called as ductility detailing or ductile detailing.
When a structure undergoes seismic forces the structure could not remain elastic anymore, and the next stage is damage. It can go through the plastic stage or fracture or damage, where stiffness will decrease appreciably and deformations will be drastically increasing even for a small load. Building design should incorporate the ductility detailing to sustain these loads without undergoing larger deformations or no collapse.
Ductility of RCC
The right grade of concrete and reinforcement steel of RCC is very important for the structural stability under dynamic condition. TMT Steel material having the right mix of moderate higher strength and higher ductility/flexibility help to absorb and distribute the energy during the earthquake. Thus steel reinforcement in the form of TMT Rebar in RCC provides the desired ductility of the buildings. This is essential in structural elements to undergo longer elongation without undergoing collapse.
Accordingly, Fe 500D TMT Rebars are most suitable and recommended for the building comes under moderate to higher seismic zones.
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