Civil Engineering is something that gives shape to one’s imagination. For developmental purposes we need to build roads, rails, ports, industries, airports, etc where the role of civil engineering comes into play. Rapid transformation of a country cannot be carried out without having a well planned and developed infrastructure which describes the very essence of a country
One such classified example of high excellence in Civil Engineering is the base isolation technique. The base isolation technique is used for protecting structures during any earthquake. Base isolation is a technique which is used by the means of rollers situated beneath any structure. The basic work of these rollers is to counter attack the earthquake forces and protect any structure from the collapse. When the ground shakes during any earthquake the rollers move but the structure does not move due to which no force is ever getting transmitted to the building so the building does not ever get affected by any scale of earthquake.
The building is basically rested on flexible pads which always offer resistance to the lateral forces. The proper selection of flexible pads reduces the impact of earthquake on the buildings. The main prospectus of base isolation is that it induces the flexibility rate in any structure apart from the normal structural collapse ratio.
The isolators are often designed to absorb the earthquake thrust and add damping to the structure. This helps in further reducing the seismic response on the structures. The base isolation technique always at a greater extent escapes the deformation and damage which signifies that the inertial forces acting on the structure had been minimized.
The ratio of impact is ¼ in the buildings with base isolators as compared to the fixed base buildings. The acceleration in the building is decreased as the base isolation technique is used to minimize the impact of vibrations.
Types of bearings-
Lead rubber bearings – These are mostly used types of bearings. A lead rubber bearing is usually made up of rubber sandwiched together with layers of steel. On the top face and bottom side the bearing is fitted with steel plates which are used to attach the lead rubber bearing to the building and foundation. The rubber type bearings are very stiff and are strong in the vertical direction but are usually flexible in the horizontal direction. The presence of lead as a crystalline material leads to the deformations beyond the yield point to regain its proper properties after the phenomenon.
High damping rubber bearings – It works on the same process of the lead rubber bearing the only difference being that high damping rubber bearings provides increased damping. A high damping rubber is actually a filled rubber compound with inherent damping properties due to the same manufacturing content but the addition of special fillers such as carbon and the resin.
As the addition of special fillers increases the inherent damping properties. The energy dissipation of this type of bearings are used for large and small strains as both are constant and are characterized by the smooth elliptical hysteresis loop, as evident in nature the typically equivalent 15% damping ratio of equivalent liner elastic models.
Hybrid type Lead high damping rubber bearing – A hybrid type of lead high damping rubber bearing consist of layers of high damping rubber placed between the steel and smaller diameter lead cylinder plug tightly in a hole. It has rigidity due to the presence of the lead plug and a dissipation mechanism due to the damping features of high damping rubber. It also allows the reduction of the initial stiffness of the isolation system which tends for higher frequency effects.
Being an important part of construction techniques, Earthquake resistant design is an important aspect in the field of Civil Engineering. As the new construction techniques being involved, a new era of multi storey or high rise buildings had begun, and had added a new dimension to civil engineering and its jobs with a much expanded future for civil engineers with the technique involved in the design and involvement of base isolators in the buildings.
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