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Polycal Wire rope isolators (PWRIs) have found many applications, especially in naval and aerospace structures. PWRIs are used to isolate individual equipment or complete floating floors against undesirable shocks and vibrations. A PWRI consists of arch shaped wire rope strands connected between circular plates. This architecture results in an isolator with a nonlinear hysteresis behavior capable of providing the necessary damping to dissipate an input energy. In this paper, a complete study of the shear cyclic behavior of PWRIs is presented. Twelve isolators of different geometries were tested in shear mode under different loading rates. The stiffness, energy dissipation, and damping were determined and related to the geometric and mechanical properties of each isolator. To overcome the limitations of existing mathematical models in representing the hysteretic behavior of wire rope isolators, a new model is proposed, in which, the Bouc-Wen-Baber-Noori model of hysteresis was adopted in conjunction with a modulating function. The model is shown to accurately replicate the soft-hardening, symmetric, hysteresis loops.

We present an enhancement to the existing elliptical leaf spring (ELS) for improved damping and energy dissipation capabilities. The ELS consists of a high tensile stainless steel elliptical leaf spring with polymer or rubber compound. This device is conceived as a shock and vibration isolator for equipment and lightweight structures. The enhancement to the ELS consists of a lead spring plugged vertically between the leaves (referred to as lead-rubber elliptical leaf spring (LRELS)). The lead is shown to produce hysteretic damping under plastic deformations. The LRELS isolator is shown to exhibit nonlinear hysteretic behavior. In both horizontal directions, the LRELS showed symmetrical rate independent behavior but undergoes stiffening behavior under large displacements. However, in the vertical direction, the LRELS behavior is asymmetric, exhibiting softening behavior in compression and stiffening behavior in tension. Mathematical models based on the Bouc-Wen model, describing the hysteretic behavior of the proposed isolator, are developed and numerically calibrated using a series of finite element analyses. The LRELS is found to be effective in the in-plane and vertical directions. The improved damping and energy dissipation of the LRELS is provided from the hysteretic damping of the lead spring.

Different isolation systems are currently employed to protect sensitive equipment and their hosting structures from undesirable vibrations originating from earthquake ground motions. Wire rope isolator (WRI), a type of passive isolator is known to be effective in isolating the vibrations and shock, can be used for vibration isolation of structures and equipment. The aim of the present work is to study the performance of WRIs in mitigating the vibrational response of equipment mounted on the upper floor of a multi-story structure using numerical simulations. In multistoried buildings, the upper floors experience significantly amplified accelerations than the lower floors and hence the sensitive equipment requires an effective vibration isolation system. The present study shows that the WRI can provide an effective isolation by reducing the equipment acceleration through its lateral flexibility while satisfying the displacement demand. The Performance of the WRI was assessed considering six different earthquake excitations in a series of numerical simulations. The influence of flexibility of the structure on the performance of the WRI is also reported.

This paper presents an analytical model for the static lateral stiffness of Wire Rope Isolators (WRI). The wire rope isolator, which is a passive isolation device, has been widely adopted as a shock and vibration isolation for many types of equipment and lightweight structures. The major advantage of the WRI is its ability to provide isolation in all three planes and in any orientation. The WRI in the lateral roll mode, is required to possess the required lateral stiffness to support and isolate the equipment effectively. The static lateral stiffness of WRI depends mainly on the geometrical characteristics and wire rope properties. The model developed in this paper is validated experimentally using a series of monotonic loading tests. The flexural rigidity of the wire ropes, which is required in the model, was determined from the transverse bending test on several wire rope cables. It was observed that the lateral stiffness is significantly influenced by the wire rope diameter and height of the isolator. The proposed analytical model can be used for the evaluation of lateral stiffness and in the preliminary design of the WRI.