Wire Rope Isolators Research Articles

Experimental study on mechanical properties of new biaxial compression wire rope isolator

<p indent=0mm>Wire rope isolator is widely used in the field of vibration isolation and shock resistance of naval equipment. To overcome the shortcomings of the poor tensile performance of the traditional wire rope isolator, a new biaxial compression wire rope isolator was designed, and the performance characteristics of the new biaxial compression wire rope isolators and spherical wire rope isolators were tested using vibration and shock test methods. By conducting a comparative experiment, the characteristics of the performance difference are studied. The frequency sweep test results show that the resonance peak of the spherical wire rope isolator is larger than that of the new one at the natural frequency. The fixed frequency test finds that the vibration performance of the new and the spherical wire rope isolator is not much different under different working conditions. The shock test results show that the shock isolation rate of the new biaxial compression wire rope isolator is above 82.5%, and the shock isolation rate in all working conditions is greater than that of the spherical wire rope isolation system, which effectively improves the tensile performance of the spherical wire rope isolator. The new biaxial compression wire rope isolator further improves the shock resistance of the vibration isolator on the basis of maintaining the original vibration isolation effect of the spherical wire rope isolator.

Numerical investigation of the seismic response of a UHV composite bypass switch retrofitted with wire rope isolators

An ultra-high voltage (UHV) composite bypass switch (BPS) faces increasing seismic challenges when UHV projects extend to high seismic intensity areas. The UHV composite BPS still generates excessive stress at the bottom section although hollow composite insulators with high flexural strength are adopted. Since the standard retrofitting strategy by using stiffer supports cannot reduce stress responses, wire rope isolation is introduced. The optimal design of isolation considers both stress and displacement responses since the slenderness and composite material of insulators contribute to significant displacement. The results show that properly designed isolation can significantly reduce stress without excessive displacement responses. A larger radius configuration helps to improve the applicability of small stiffness isolators under high winds. When the isolation still cannot satisfy the requirement, smaller stiffness isolators with a larger radius, or isolators with increased loops and smaller radius, can be introduced to gain better energy dissipation capacity and effectiveness in response mitigation. Accordingly, a three-step design procedure is proposed to increase the damping force but fix the rotational stiffness of isolation. Hence, the application of wire rope isolation can be extended to UHV composite BPS with a low natural frequency, but conductors with enough redundancy should be used.

Behavior of polycal wire rope isolators subjected to large lateral deformations

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.

Lateral stiffness of polycal wire rope isolators – An experimental study

The PWRI is a type of passive isolation system which is commonly used as shock and vibration isolation system especially applied in lightweight equipment and electronic devices. The PWRI can provide isolation in all direction. It can be flexible in any direction and in all three planes which depends on its stiffness. An experimental study of the lateral stiffness of Polycal Wire Rope Isolators (PWRI) is presented in this paper. It also studied effect of variations in height and width of PWRI on its static stiffnesses. Suitable experimental setup was designed and manufactured to meet the test conditions. The results show that their elastic stiffnesses for lateral loading conditions are highly influenced by their geometric dimensions. It is found that their compressive stiffness reduced by 56% for an increment of 25% in their height to width ratio. Therefore, the stiffness of PWRI can be fine-tuned by controlling their dimensions according to the requirements of the application.

Effect of Structure Parameters on Polycal Wire Rope Isolator Stiffness‐Damping Characteristics

Wire rope isolators are mainly used to isolate vibration and protect precise equipment. However, the issue of regulation of vibration isolators taking into account the nonlinearity of their characteristics was poorly understood in the modern literature. In this paper, the influence of structural parameters (diameter ratio and lay pitch of the single strand, and lay pitch and bending radius of the wire rope) on stiffness‐damping characteristics of the Polycal WRI was investigated by the simplified finite element analysis method. The stiffness and damping prediction models including structural parameters and material properties were established. The results showed that the stiffness‐damping characteristics were the best; when the diameter ratio of wire strand was 1.1, the inside layer wire pitch length was 6 times the diameter of the wire strand, the outside layer wire pitch length was 11 times the diameter of the wire strand, the pitch length of the wire rope was 7.5 times its diameter, and the bending radius was equal to 46.5 mm. The errors of the prediction for prestiffness and softened stiffness were within 5%, and the errors of prediction for the energy dissipation coefficient were within 10%.

Stiffness characteristics of a polycal wire rope isolators

Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The source of vibrations can be either natural or man-made. The vibrations caused by such source affect the operation of heavy machines and structures. Polycal Wire rope isolator (PWRI), a type of passive isolator can be used to attenuate the harmful effects of vibration. The main advantage of PWRI is that isolation in all the directions and in all planes can be provided. For a given mass, the key to achieve isolation is by reducing the natural frequency of the system lower than the excitation frequency. This is achieved by applying a flexible isolators and hence, the stiffness of the isolator plays a major role in the isolation applications. In this study, stiffness characteristics of polycal wire rope isolators are determined through experimental and numerical work. The numerical model of the polycal WRI is developed following the equivalent diameter approach using the flexural rigidity of the wire rope. It was found that the wire rope diameter greatly influences the stiffness of a PWRI. This work will enhance the understanding of the wire rope isolator for vibration isolation applications.

Seismic response of steel structures with wire rope isolators at base

In this paper, cable isolators with applications in the field of vibration and shocks imported into steel structures and isolated equipment are investigated. The aim of this study is to examine the effect of wire rope isolators by combining friction isolators in steel structures, as well as to obtain the seismic response of isolated structures at base, and to investigate the effect of this isolator on the seismic response based on the nonlinear time history analysis which is the method of our research. Incremental Dynamic Analysis (IDA) is used to evaluate the seismic capacity demand of steel moment frames. In the IDA, spectral acceleration at the first-mode period of vibration with 5 percent damping (Sa(T1, 5 %)) has been used as an Intensity Measure (IM) , which has the less dispersion for far-fault records. The fragility curves of the structures have been presented for different performance levels.

Wire Rope Isolators for Seismic Base Isolation

Tall and slender substation equipment is prone to failure under seismic excitations. The consequences of such failure can be devastating and lead to weeks or months of lost power. The IEEE Std 693-2005 ensures that all substation equipment installed in high seismic areas are designed to withstand earthquakes of a severity related to that area. There are numerous ways to increase the seismic strength of substation equipment and this paper will discuss doing so by base isolation, specifically using wire rope isolators (WRIs). It is the purpose of this paper to present a case study in which the Socitec Group provided a WRI base isolation design for a high voltage surge arrester. The simulation results show that the moment at the base of the surge arrester was reduced by 55% when using the Socitec designed WRI base isolation system.

Influence and Enhancement of Damping Properties of Wire Rope Isolators for Naval Applications

Influence and Enhancement of Damping Properties of Wire Rope Isolators for Naval Applications

Experimental and numerical vibration analysis of wire rope isolators under quasi-static and dynamic loadings

Wire rope isolators have applications for vibration isolation in many industrial machinery and precise equipment. In this paper, the dynamic characteristics of an industrial wire rope isolator are investigated. A series of experiments were carried out on the isolator for quasi-static and dynamic loadings. Both horizontal and vertical excitations were considered. Next, a modified Bouc-Wen model was used to predict the behavior of the wire rope isolator under quasi-static loads. To have a comprehensive model able to predict the behavior of the isolator in all loading conditions, an artificial neural network model was proposed. The model was trained with a set of data and after convergence; it was used for prediction of some experimental cases which were not used in the training process. The obtained results indicate that the neural network model can predict the hysteresis behavior of the wire rope isolator with a good degree of accuracy.

Experimental study on vertical static stiffnesses of polycal wire rope isolators

Wire rope isolator is one of the most effective isolation system that can be used to attenuate the vibration disturbances and shocks during the operation of machineries. This paper presents the results of investigation on static elastic stiffnesses (both in tension and in compression) of Polycal Wire Rope Isolator (PWRI) under quasi-static monotonic loading conditions. It also studied effect of variations in height and width of PWRI on its static stiffnesses. Suitable experimental setup was designed and manufactured to meet the test conditions. The results show that their elastic stiffnesses for both tension and compression loading conditions are highly influenced by their geometric dimensions. It is found that their compressive stiffness reduced by 55% for an increment of 20% in their height to width ratio. Therefore, the stiffness of PWRI can be fine-tuned by controlling their dimensions according to the requirements of the application.

Wire rope isolators for seismically base-isolated lightweight structures: Experimental characterization and mathematical modeling

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.

Performance of wire rope isolators in the seismic protection of equipment

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.

Static lateral stiffness of wire rope isolators

ABSTRACTThis 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.

An analytical study on the static vertical stiffness of wire rope isolators

The vibrations caused by earthquake ground motions or the operations of heavy machineries can affect the functionality of equipment and cause damages to the hosting structures and surrounding equipment. A Wire rope isolator (WRI), which is a type of passive isolator known to be effective in isolating shocks and vibrations, can be used for vibration isolation of lightweight structures and equipment. The primary advantage of the WRI is that it can provide isolation in all three planes and in any orientation. The load-supporting capability of the WRI is identified from the static stiffness in the loading direction. Static stiffness mainly depends on the geometrical and material properties of the WRI. This study develops an analytical model for the static stiffness in the vertical direction by using Castigliano’s second theorem. The model is validated by using the experimental results obtained from a series of monotonic loading tests. The flexural rigidity of the wire ropes required in the model is obtained from the transverse bending test. Then, the analytical model is used to conduct a parametric analysis on the effects of wire rope diameter, width, height, and number of turns (loops) on vertical stiffness. The wire rope diameter influences stiffness more than the other geometric parameters. The developed model can be accurately used for the evaluation and design of WRIs.

Experimental investigation on the hysteresis behavior of the wire rope isolators

Vibration isolation has been widely applied to filter the external excitation energy and impact forces in building structures and equipment. Wire rope isolator (WRI), a kind of isolator for vibration and shock isolation, shows a better performance in attenuating these forces. WRIs are able to deviate these external forces through their mechanical configuration and high-energy dissipative capabilities. The application of WRI demands knowledge of its behavior and the relation between various geometrical properties and input force. The present work investigates the influence of geometrical parameters, such as wire rope diameter, number of coils, and displacement amplitude on the hysteresis behavior of WRI under quasi-static loading in both vertical and horizontal directions. The hysteresis behavior of different WRIs was evaluated using the calculated parameters from hysteresis force-displacement curves: energy loss ratio (ELR), and effective stiffness. The study indicates that the geometric properties significantly influence the effective stiffness than the energy loss ratio. It is observed that, increased displacement amplitude results in decreased ELR and hence damping capabilities. The study also confirms that the wire rope isolator possesses a good ability in damping through its stiffness and high-energy dissipation capability.

Seismic retrofitting of an HV circuit breaker using base isolation with wire ropes. Part 1: Preliminary tests and analyses

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.

Seismic retrofitting of an HV circuit breaker using base isolation with wire ropes. Part 2: Shaking-table test validation

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.

Wire rope isolators for vibration isolation of equipment and structures – A review

Vibrations and shocks are studied using various techniques and analyzed to predict their detrimental effect on the equipment and structures. In cases, where the effects of vibration become unacceptable, it may cause structural damage and affect the operation of the equipment. Hence, adding a discrete system to isolate the vibration from source becomes necessary. The Wire Rope Isolator (WRI) can be used to effectively isolate the system from disturbing vibrations. The WRI is a type of passive isolator that exhibits nonlinear behavior. It consists of stranded wire rope held between two metal retainer bars and the metal wire rope is made up of individual wire strands that are in frictional contact with each other, hence, it is a kind of friction-type isolator. This paper compiles the research work on wire rope isolators. This paper presents the research work under two categories, namely monotonic and cyclic loading behaviors of WRI. The review also discusses the different terminologies associated with vibration isolation system and highlights the comparison between various isolation systems.

Vibration Behavior Analysis of Wire Rope Isolators Under Traction and Compression Load

In this paper, based exclusively on measurements, is presented a study about the vibration behavior of wire rope isolators (WRI) used in a specific application of vibration attenuation of the exhaust line. The objective of this study was to make a comparative analysis between the vibration attenuation performances of these isolators subjected by the exhaust line to traction or compression load. The analysis results will help us find out which one of these mounting methods highlights best the isolators' vibration damping properties.