About the Forces and Moments that Influence the Behavior …
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Fig. 2 5-story building isolated with friction pendulums
Designing seismic systems generally involves analyzing how the structure
responds to a seismic action, but also defining the system acceleration to determine
the period T in which the isolated structure oscillates [5].
The relationship of equivalent stiffness calculation is:
T = 2π
G
k ech
(2)
where by the equivalent stiffness results as:
k ech =
2π
T 2
· G
(3)
The aim of seismic isolators is to increase the flexibility of the base by reducing the
acceleration transmitted to the structure by the seismic motion. Thus, if the variation
of the forces and displacements acting on the construction compares, it is observed
that changing the vibration period to the increase of the movement at the level of the
structure base will decrease the forces acting on it [6].
The normal force N, which is composed of the static load G, the acceleration effect
ü, and the additional seismic load due to the torque M, acts on the sliding surfaces
Fig. 3.
Normal force N is given by: