454
I. Goł˛ ebiowska and M. Dutkiewicz
The problem of designing of effective devices to reduce vibration caused by
seismic impacts lies in the unique and difficulties in description of the nature of such
excitations. Hence, an important role is played by the probabilistic description, in
particular the probabilistic approach to excitation variability. Bucher [12] developed
the probability-based optimization of friction damping devices.
Isolation bearings are used in engineering structures of various types, e.g., in buildings, bridges, tanks, industrial facilities. Elastomeric and sliding bearings are the two
main groups of insulation devices. Rubber used to isolate structures against vibrations
from the ground is used in elastomeric bearings, while low rigidity and friction at
the joint, mainly between stainless steel and Teflon are the features that characterize
sliding bearings. High axial stiffness for transferring vertical loads without excessive
deformation, sufficiently low horizontal stiffness, so that the first natural frequency
of the isolated structure is significantly lower than the dominant frequency of the
expected ground movement, an effective energy dissipation mechanism, contributing
to the reduction of excessive horizontal (lateral) displacements seismic isolation
against variable permanent load are the features that seismic isolation devices have.
The paper discusses friction pendulum bearings, taking into account the criterion
of energy dissipation efficiency in engineering facilities. In addition, the example of
the experiment is the valuable enrichment of this review.
2 Friction Pendulum Bearing Supports
The analyzed group of devices includes isolation bearings defined as Pure-Friction
(PF) and the Friction Pendulum (FP) bearing. In a PF bearing, two horizontal flat
stainless steel plates slide on top of each other. During an earthquake, the structure
moves on the upper insulator plate. This type of insulator will not experience resonance frequency. The second isolation device is Friction Pendulum (FP) proposed
by Zayas [13].
The base-plate and the slider covered by the composite material are the basic
elements of FP bearing, which uses the mechanism of pendulum and the frictional
sliding. A restraining rim around the edge of the sliding surface is a solution to limit
the displacement (Fig. 1).
There are two design methods using friction pendulum. The P-D effect transfer
downward to the structure below the isolation system or upward to the elements of
the superstructure.
Soong and Constantinou [14] propose the formula:
F = W
x
R
+ µsgn( ˙
x)
,
(1)
where W —isolator’s normal force, R—the spherical curvature’s radius, x—horizontal displacement of the slider’s pivot, ˙
x—velocity of sliding, µ—coefficient of
friction.
I. Goł˛ ebiowska and M. Dutkiewicz
The problem of designing of effective devices to reduce vibration caused by
seismic impacts lies in the unique and difficulties in description of the nature of such
excitations. Hence, an important role is played by the probabilistic description, in
particular the probabilistic approach to excitation variability. Bucher [12] developed
the probability-based optimization of friction damping devices.
Isolation bearings are used in engineering structures of various types, e.g., in buildings, bridges, tanks, industrial facilities. Elastomeric and sliding bearings are the two
main groups of insulation devices. Rubber used to isolate structures against vibrations
from the ground is used in elastomeric bearings, while low rigidity and friction at
the joint, mainly between stainless steel and Teflon are the features that characterize
sliding bearings. High axial stiffness for transferring vertical loads without excessive
deformation, sufficiently low horizontal stiffness, so that the first natural frequency
of the isolated structure is significantly lower than the dominant frequency of the
expected ground movement, an effective energy dissipation mechanism, contributing
to the reduction of excessive horizontal (lateral) displacements seismic isolation
against variable permanent load are the features that seismic isolation devices have.
The paper discusses friction pendulum bearings, taking into account the criterion
of energy dissipation efficiency in engineering facilities. In addition, the example of
the experiment is the valuable enrichment of this review.
2 Friction Pendulum Bearing Supports
The analyzed group of devices includes isolation bearings defined as Pure-Friction
(PF) and the Friction Pendulum (FP) bearing. In a PF bearing, two horizontal flat
stainless steel plates slide on top of each other. During an earthquake, the structure
moves on the upper insulator plate. This type of insulator will not experience resonance frequency. The second isolation device is Friction Pendulum (FP) proposed
by Zayas [13].
The base-plate and the slider covered by the composite material are the basic
elements of FP bearing, which uses the mechanism of pendulum and the frictional
sliding. A restraining rim around the edge of the sliding surface is a solution to limit
the displacement (Fig. 1).
There are two design methods using friction pendulum. The P-D effect transfer
downward to the structure below the isolation system or upward to the elements of
the superstructure.
Soong and Constantinou [14] propose the formula:
F = W
x
R
+ µsgn( ˙
x)
,
(1)
where W —isolator’s normal force, R—the spherical curvature’s radius, x—horizontal displacement of the slider’s pivot, ˙
x—velocity of sliding, µ—coefficient of
friction.