Author(s)

N. Makris

Abstract

This paper examines the problem of protecting flexible structures from rapid, long-period motions. Recent records from near-source earthquakes have created concerns about the vulnerability of flex- ible structural systems such as base isolated structures. First, a comprehensive analytical study is developed which shows that the presence of friction type forces (rigid-plastic behavior) reduces substantially displacements by keeping accelerations (base shears) at low levels. However, in some cases the presence of high friction forces in the isolation system of a structure are responsible for permanent displacements of the superstructure. Electrorheological dampers and other semi-active dampers can in principle supply the friction type forces needed at the beginning of the

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