Influence of Displacement Amplitude and Vertical Load on the Horizontal Dynamic and Static Behavior of Helical Wire Rope Isolators

In this paper, the results of experimental tests
performed on a Helical Wire Rope Isolator (HWRI) are presented in
order to describe the dynamic and static behavior of the selected
metal device in three different displacements ranges, namely small,
relatively large, and large displacements ranges, without and under
the effect of a vertical load. A testing machine, allowing to apply
horizontal displacement or load histories to the tested bearing with a
constant vertical load, has been adopted to perform the dynamic and
static tests. According to the experimental results, the dynamic
behavior of the tested device depends on the applied displacement
amplitude. Indeed, the HWRI displays a softening and a hardening
stiffness at small and relatively large displacements, respectively, and
a stronger nonlinear stiffening behavior at large displacements.
Furthermore, the experimental tests reveal that the application of a
vertical load allows to have a more flexible device with higher
damping properties and that the applied vertical load affects much
less the dynamic response of the metal device at large displacements.
Finally, a decrease in the static to dynamic effective stiffness ratio
with increasing displacement amplitude has been observed.

Authors:

• Nicolò Vaiana
• Mariacristina Spizzuoco
• Giorgio Serino

Keywords:

• Base isolation
• earthquake engineering
• experimental hysteresis loops
• wire rope isolators.

References:

[1] M. L. Tinker and M. A. Cutchins, “Damping phenomena in a wire rope
vibration isolation system,” Journal of Sound and Vibration, vol. 157,
no. 1, pp. 7-18, 1992.
[2] G. F. Demetriades, M. C. Constantinou and A. M. Reinhorn, “Study of
wire rope systems for seismic protection of equipment in buildings,”
Engineering Structures, vol. 15, no. 5, pp. 321-334, 1993.
[3] G. Serino, F. Bettinali and G. Bonacina, “Seismic base isolation of gas
insulated electrical substations: comparison among different solutions,”
Proceedings of the 4th US Conference on Lifeline Earthquake
Engineering, San Francisco, California, 1995.
[4] G. Serino, G. Bonacina and F. Bettinali, “Passive protection devices for
high-voltage equipment: design procedures and performance
evaluation,” Proceedings of the 4th US Conference on Lifeline
Earthquake Engineering, San Francisco, California, 1995.
[5] M. Di Donna and G. Serino, “Base isolation of high-voltage equipment:
comparison between two different solutions,” Proceedings of the 7th
International Conference on Probabilistic Methods Applied to Power
Systems, Napoli, Italy, 2002.
[6] S. Alessandri, R. Giannini, F. Paolacci and M. Malena, “Seismic
retrofitting of an HV circuit breaker using base isolation with wire ropes.
Part 1: Preliminary tests and analyses,” Engineering Structures, vol. 98,
pp. 251-262, 2015.
[7] G. De Canio, “Marble devices for the base isolation of the two bronzes
of Riace: a proposal for the David of Michelangelo,” Proceedings of the
15th Word Conference on Earthquake Engineering, Lisbon, Portugal,
2012.
[8] S. Alessandri, R. Giannini, F. Paolacci, M. Amoretti and A. Freddo,
“Seismic retrofitting of an HV circuit breaker using base isolation with
wire ropes. Part 2: Shaking-table test validation,” Engineering
Structures, vol. 98, pp. 263-274, 2015.
[9] S. Pagano, M. Russo, S. Strano and M. Terzo, “A mixed approach for
the control of a testing equipment employed for earthquake isolation
systems,” Journal of Mechanical Engineering Science, vol. 228, no. 2,
pp. 246-261, 2014. [10] A. K. Chopra, Dynamics of Structures: Theory and Applications to
Earthquake Engineering, 4th ed. Englewood Cliffs, NJ: Prentice Hall,
2012.