Seismic energy wave is the outburst of energy created during tectonic movement of earth crust and large man-made explosions which generate low-frequency acoustic energy. Seismic energy and its corresponding effects strongly impact the structural stability of a structure and possess severe threat to human life. Specific scientific techniques are adopted to provide structural safety and comfort by controlling the internal forces and displacement within the particular limits. One of the most common method for protecting structures against destructive effects of earthquakes is to damp the seismic energy by the structural elements like seismic mounts. These isolators provide adequate resistance to the undesired vibrations. This method offers certain level of protection however; there is a probability of structure being damages when exposed to critical situations. To overcome this scenario another method for protection of the structures against the seismic energy is to isolate the structure by installing seismic isolators whose function is to dissipate the energy and restrict transfer of vibrations from source to structures.
Seismic isolation is a technique used to reduce the effects of earthquake on structure, their components and protect them from damaging. It effectively decouples a supporting structure from mounting structure grouted on a shaking ground thus protecting a building or a structure’s integrity, stability and strength. Seismic isolators offer much better protection as it isolates the vibrating source and dissipates the energy internally, thus providing significant structural protection. The seismic isolators and energy dissipating devices are seen to be an effective solution. They are installed in the structure to damp the seismic energy or placed between the foundation and vertical structural systems to provide the desired result.
Seismic isolator dampens the undesired seismic energy under the ground of the structure, thus decreasing the effects of lateral loads on the above surface. As defined in physics that when external seismic forces are exerted on any structure mounted on floor, its stability is governed by its mass, stiffness and energy damping characteristics. Response or stability of structure can be controlled by changing stiffness of structure. Higher the damping effect of building lesser is the reaction towards undue acceleration and displacements. Today there are two types of seismic isolators available which include seismic spring isolators and seismic mounts that are installed in a structure to offer stability and desired strength.
Isolators amend the dynamic characteristics of the structural system by changing total mass and the distribution of mass within structure. They act as energy dissipating mechanism and are classified in two major categories depending on their location and operating principles. When we focus on location wise seismic isolators they are generally categorised under the head of externally mounted seismic isolators and internally mounted seismic isolators. As the name suggests, external type seismic mounts are installed outside the structural location and cater to provide isolation externally through foundation of structure. Whereas, internal type seismic mounts act as an energy dissipating mechanism that provides internal stability through effective isolation. Natural disaster like earthquake cannot be prevented and is beyond human control but eliminating the potential damage by taking the precautions against the natural calamity is possible through equipment’s like seismic isolators.