Base isolation

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Snapshot of shake-table testing of a base-isolated (right) and a regular (left) building model at UCSD

Base Isolation is believed to be 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, 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 (see, e.g., the concurrent shake-table crash testing video on Earthquake Protector). For this, some pads are inserted into all major load-carrying elements in the base of the structure. It also requires creating a rigidity diaphragm and a moat around the structure, as well as making provisions against its overturning and P-delta effect.

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.

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].

Base isolation demonstration at The Field Museum. Courtesy of Irena Knezevic [1]

The first evidence of earthquake protection by using the principle of Base Isolation was discovered in Pasargadae, a city in ancient Persia, now Iran: it goes back to VI century BC.

This technology can be used both for new structural design [4] and seismic retrofit. In process of seismic retrofit, some of the most prominant U.S. monuments like, e.g., Pasadena City Hall, San Francisco City Hall or Salt Lake City and County Building were mounted on Base Isolation Systems.

Base Isolation can be also used as a valuable reinforcement of Dispensable Structural System [5] for Blast Debris Protection [6].

Analytical research software called Earthquake Performance Evaluation Tool (EPET), which is publicly accessible online, enables concurrent virtual experiments on the building models with and without Base Isolation.

[edit] External Links

1. The Field Museum 2. Lead Rubber Bearing being tested at the UCSD Caltrans-SRMD facility. 3. Hybrid Simulation of Base Isolated Structures. 4. Seismic Isolation Projects in Japan. 5. Sails-Rigging Blast Protective Structural Shield, SEAINT. 6. Terrorist Blast Protection: Dispensable Structural System Reinforced with Earthquake Buffer, ASCE.