Question

Why must the lateral tangential stiffness of a base isolator remain positive?

Answer 1

Base isolation is process in which For reducing the seismic demand large displacements are allowed to occur at flexible horizontal elements which are introduced at the foundation level of structure .

For large displacements horizontal stiffness must be low . But vertical stiffness must be larger for sufficient support of weight of the structure and to minimise potential Rocking motions.

Lateral tangential stiffness of a base isolator must be remain positive because it shows stable roller deformation.