Base Isolation


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Conventional Construction Practice assumes Fixed Base Structures


The Dynamic Characteristics of Fixed Base Structures are determined by the general characteristics of the structural system

The Designer can only slightly adjust those Dynamic Characteristics

As a matter of fact, most common Building Structures have unfavorable Dynamic Characteristics that result in increased Seismic Response

The Concept of Base Isolation

Significantly Increase the Period of the Structure and the Damping so that the Response is Significantly Reduced

How exactly does Base Isolation Work?

Most types of Isolators exhibit nonlinear behavior

Lengthening of the Structure’s Period and increased Damping that result in a large scale decrease of the Seismic Response

Oakland City Hall


Building was severely damaged during the 1989 Loma Prieta earthquake
Building is listed on the historic register – Retrofit had to preserve the interior architecture and the historic fabric of the building
Both conventional fixed-base and base isolation retrofit concepts were studied
The most economical and effective method was determined to be base isolation