Search

The results of an extensive series of dynamic and static experimental tests conducted on four Wire Rope Isolators (WRIs) under different values of vertical load are presented. The main aim of this work is identifying the mechanical characteristics of WRIs in three displacements ranges, that is, small, relatively large and large displacements ranges, to allow the use of these metal devices in the base isolation system of seismically base-isolated lightweight structures. In order to simulate the dynamic behavior of WRIs in the two principal horizontal directions, namely, Roll and Shear directions, a one dimensional (1d) Nonlinear Exponential Model, able to simulate the increase of the tangent stiffness observed at larger displacements, is proposed. Compared to the widely used Bouc-Wen model, the proposed one does not require the numerical solution of a first order ordinary nonlinear differential equation, thus decreasing the computational effort of nonlinear time history analyses, and contains a smaller number of parameters to be identified. The mathematical model has been validated by comparing the experimental hysteresis loops obtained during cyclic tests with those predicted analytically. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wire Rope Isolators (WRIs) guarantee high values of dissipated energy and damping. • Stiffening and softening behaviour have been exhibited. • The influence of the axial preload is negligible in terms of dissipated energy. • A new hysteretic model is shown to accurately reproduce the hysteretic behaviour of WRIs. An experimental campaign aiming to study the dynamic response of four different helical Wire Rope Isolators (WRIs) loaded along the axial direction is described in the paper. A total of seventy-one tests have been carried out by applying as input, to each of them, ten cycles of sinusoidal displacement. Specifically, the dynamic response of the WRIs has been analysed by varying input properties, such as amplitudes and frequencies, and simulated by means of a recently developed hysteretic model derived from a new class of uniaxial phenomenological models. For completeness, the influence of the axial preload as well as of the wire rope diameter on the dynamic behaviour of the tested WRIs is also discussed. In particular, a close agreement between predicted hysteresis loops, having asymmetric shape, and experimental ones has been achieved. [ABSTRACT FROM AUTHOR]

This paper briefly describes the design and characterisation of a base isolation system that protects HV ceramic circuit breakers during seismic events. This qualifies them to the European standard CEI EN 62271-207. The solution is based on an innovative application of wire rope isolators. Preliminary numerical analyses and tests were performed on a typical HV circuit breaker and demonstrated the effectiveness of the proposed isolation system in reducing seismic demand. The results were also validated using a shaking table, which is described in an accompanying paper. The on-site installation of this system in several Italian substations has finally proved simple enough to upgrade the equipment for seismic protection. [ABSTRACT FROM AUTHOR]

This paper addresses the experimental characterisation of a base-isolation system for the seismic qualification, of High Voltage (HV) ceramic circuit breakers, in accordance with the European standard CEI EN 62271-207. The adopted solution is based on an innovative application of wire rope isolators. The results of a preliminary investigation of an HV circuit breaker, which was base-isolated with wire ropes, were previously illustrated in a companion paper in which the effectiveness of this isolation system was analytically demonstrated. To validate these results, a shake table test campaign has been performed that includes the performance analysis of two optimal isolation system configurations. The results, which are illustrated in this paper, show both the effectiveness of this isolation system and the reliability of the proposed FE model. [ABSTRACT FROM AUTHOR]