9īased on their main properties and compounds there are two sorts of elastomeric bearings: Natural and Synthetic Rubber Bearings and Lead Rubber Bearings. The first use of a rubber isolation system to protect a structure from earthquakes was in 1969 for an elementary school in Skopje, Yugoslavia. In their case the vibration energy flow is directed from the machine towards the foundation that has to be protected. These types of devices have been used, before being applied in civil engineering, to isolate vibrating machines. There are two basic types of base isolator devices( elastomeric bearing and Friction pendulum bearing systems) and some supplementary devices for them. 3: Effects of base isolation: a) on spectral acceleration, b) on lateral displacement, c) for different soil conditions In stiff soil conditions a significant reduction in spectral acceleration is attained while in soft soil the adverse occurs - fig.3c) 6,7įig. The local soil conditions have a great impact on the reliability of the base isolation. The damping by energy dissipation influences the displacement and the acceleration response as it is shown in the schemes 3a), and 3b). The seismic isolation system is used in order to decrease the earthquake energy (E) acting on the structure. Is the elastic strain, Eh is the hysteretic damping energy, Ev is the viscous damping energy. Where E is the energy induced by the seismic shaking, Ek is the kinetic energy, Es 5 Isolators reduce the energy of structure too. This gives the structure a fundamental frequency that is much lower than both its fixed-base frequency and the predominant frequencies of the ground motion. The system decouples the building or structure from the horizontal components of the ground motion by interposing structural elements with low horizontal stiffness between the structure and the foundation. 2: concept of seismic isolation for buildings 1: Building with and without seismic isolators Acceleration vs. So increase the frequency and reduce forces applied to floors according to Newton second law and following formulas.įig. These hardwires reduce the period and acceleration of structure. In this technique we use some hardwires that I will describe later to reduce structures lateral movement(Drift). Seismic isolation is a technique used to reduce the effects of earthquake ground shaking on structure, their components and protect them from damaging.
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