Base isolation, also known as seismic or base isolation system, is a collection of structural elements which should substantially decouple a superstructure from its substructure resting on a shaking ground thus protecting a building or non-building structure's integrity [1].
Base isolation is the most powerful tool of the earthquake engineering pertaining to the passive structural vibration control technologies. It is meant to enable a building or non-building structure to survive a potentially devastating seismic impact through a proper initial design or subsequent modifications. In some cases, application of base isolation can raise both a structure's seismic performance and its seismic sustainability considerably.
Base isolation system consists of isolation units with or without isolation components, where:
1. Isolation units are the basic elements of base isolation system which are intended to provide the mentioned decoupling effect to a building or non-building structure.
2. Isolation components are the connections between isolation units and their parts having no decoupling effect of their own.
By their response to an earthquake impact, all isolation units may be divided into two basic categories: shear units [2] and sliding units [3]. The first evidence of architects using the principle of base isolation for earthquake protection was discovered in Pasargadae, a city in ancient Persia, now Iran: it goes back to VI century BC.
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This technology can be used both for new structural design [5] and seismic retrofit. In process of seismic retrofit, some of the most prominent U.S. monuments like, e.g., Pasadena City Hall, San Francisco City Hall, Salt Lake City and County Building or LA City Hall were mounted on Base Isolation Systems. It required creating rigidity diaphragms and moats around the buildings, as well as making provisions against overturning and P-delta effect.
See also
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- Earthquake engineering structures
- Elevated building foundation
- Geotechnical engineering
- Household seismic safety
- Seismic retrofit
References
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