Introduction to Seismic Isolation Technology:

Seismic Isolation Technology protects buildings, bridges, and heavy mechanical components from destructive earthquake-induced forces. This technology decouples buildings from the earthquake ground motions by creating a flexible interface between them. This flexible interface, often called the isolation interface, elongates the fundamental period of the isolated structure. It enhances its dynamic performance by concentrating the earthquake-induced lateral displacements at the isolation interface and effectively reducing and preventing the transfer of earthquake energy to the superstructure.

Technical Concept and Fundamentals of the Seismic Isolation System

Seismic isolation systems will increase the horizontal fundamental period of the structure. This increase is significant since the fundamental period of an isolated structure will be in a range dissimilar to the predominant period of the earthquake-induced ground motion. As a result, the energy transmitted to the isolated structure will decrease considerably. This phenomenon is demonstrated in Figures 1.6 (a) and (b). With close attention to the following seismic response spectra, the philosophy behind the installation of base isolators can be stated as follows: to lengthen the period of vibration of the protected structure, to reduce the base shear induced by the earthquake, while providing additional damping to reduce the relative displacements across the isolators themselves. This is why most seismic design codes suggest the use of base isolation systems that have the dual function of period elongation and energy dissipation. Structures are not normally isolated from vertical earthquake ground motion. In general, the vertical earthquake ground motion is of a smaller magnitude than horizontal ground motion, and since structures are designed to withstand static gravity loads, they are inherently stiff enough in the vertical direction, making the vertical isolation component of secondary importance. The fundamental frequencies of low-rise buildings most often fall within the horizontal ground motion of most earthquakes’ predominant frequency range and consequently make them more vulnerable. Thus, the application of seismic isolation systems to low-rise buildings could play an important role in seismic design and protection (Reference; Adib Natanzi the founder of Ph.D thesis)

Deformation Pattern- Conventional Fix-based & Isolated Building During Intensive Earthquake