Abstract:
Base isolation has been used in many classes of civil engineering structures to reduce the damage
from earthquake attacks. The main idea behind this innovative technique is to shift the fundamental
natural frequency of the structure to a value much lower than the dominant frequency of the
earthquake. In this work, dynamic characteristics of a five-storey benchmark model isolated with
laminated rubber bearings (LRB) and Lead core rubber bearings (LCRB) under Kobe and El-Centro
ground motions were examined using a shaking table. The earthquake resistant performance of LRB
and LCRB isolators was evaluated. The first natural frequency of the model was reduced from 4.7Hz
for the unisolated model to 2.9 and 1.7 Hz for the LRB and LCRB isolated models, respectively. It
was observed that maximum floor accelerations were significantly reduced with the addition of an
LRB or LCRB isolation system regardless of the ground motion input. However, the LRB was
identified to be :more effective than LCRB in reducing accelerations and model relative
displacements, and therefore, provided a better protection of the superstructure and its contents. On
the other hand, the LCRB produced smaller base and floor displacements, and hence can ensure
structural stability better than the LRB. This property of LCRB stems from high damping and
stiffness of the lead core.
