Hysteresis Loops of Base Isolation System - An Overview

2021 ◽  
Vol 879 ◽  
pp. 189-201
Author(s):  
M.A. Amir ◽  
N.H. Hamid
Keyword(s):  
Earthquake Engineering ◽  
Structural Damage ◽  
Base Isolation ◽  
Numerical Models ◽  
Hysteresis Loops ◽  
Human Beings ◽  
Rc Buildings ◽  
Isolation System ◽  
Base Isolation System ◽  
Isolation Systems

Recently, there are a lot of technological developments in the earthquake engineering field to reduce structural damage and one of them is a base isolation system. The base isolation system is one of the best technologies for the safety of human beings and properties under earthquake excitations. The aim of this paper is to review previous research works on simulation of base isolation systems for RC buildings and their efficiency in the safety of these buildings. Base isolation decouples superstructure from substructure to avoid transmission of seismic energy to the superstructure of RC buildings. The most effective way to assess the base isolation system for RC building under different earthquake excitations is by conducting experiment work that consumes more time and money. Many researchers had studied the behavior of base isolation system for structure through modeling the behavior of the base isolation in which base isolator is modeled through numerical models and validated through experimental works. Previous researches on the modeling of base isolation systems of structures had shown similar outcomes as the experimental work. These studies indicate that base isolation is an effective technology in immunization of structures against earthquakes.

scholarly journals Polymeric Bearings as a new base isolation system suitable for mitigating machine-induced vibrations

2018 ◽  
Vol 211 ◽  
pp. 17001 ◽  
Author(s):  
Tomasz Falborski ◽  
Robert Jankowski
Keyword(s):  
Base Isolation ◽  
Excitation Frequency ◽  
Hysteresis Loops ◽  
Shaking Table ◽  
Damping Properties ◽  
Structural Vibrations ◽  
Isolation System ◽  
Equivalent Damping ◽  
Flexible Polymer ◽  
Base Isolation System

The present paper summarizes the preliminary results of the experimental shaking table investigation conducted in order to verify the effectiveness of a new base isolation system consisting of Polymeric Bearings in reducing strong horizontal machine-induced vibrations. Polymeric Bearing considered in the present study is a prototype base isolation system, which was constructed with the use of a specially prepared flexible polymer with improved damping properties. Dynamic oscillatory tests, during which a concrete base slab supported by four Polymeric Bearings was subjected to horizonal sinusoidal excitations characterized by different frequencies and amplitudes, were conducted in order to determine the damping properties of Polymeric Bearings and their effectiveness in mitigating structural vibrations. Equivalent damping ratios for every excitation frequency considered were determined using the experimentally obtained hysteresis loops. Final conclusions are presented and the results discussed.

scholarly journals Research on Seismic Response of Base-Isolated Nuclear Island Building considering FSI Effect of PCS Water Tank

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Chenning Song ◽  
Chao Wei ◽  
Zhi Zhang
Keyword(s):  
Seismic Response ◽  
Base Isolation ◽  
Numerical Models ◽  
Horizontal Displacement ◽  
Reduction Ratio ◽  
Isolation Effect ◽  
Water Tank ◽  
Isolation System ◽  
Base Isolation System ◽  
Natural Frequency Analysis

Base isolation can be used to reduce seismic response of structure and protect the structure from damage subjected to earthquake. To study the isolation effect of new PWR nuclear power plant with a base isolation system, considering FSI (fluid-structure interaction) effect by the simplified model, two 3D numerical models (one nonisolated model and one isolated model) were established. After natural frequency analysis, one artificial ground motion was chosen to analyze isolation effect qualitatively. Based on the results, the accelerations and relative displacements of nuclear island building under ten natural ground motions were statistically analyzed to evaluate the isolation effect quantitatively. The results show that the base isolation system can reduce the natural frequencies of nuclear island building. Horizontal accelerations can be reduced effectively, but the isolation effect is not obvious in vertical direction. The acceleration reduction ratio of the top is about 70%–90%, and the acceleration reduction ratio of the lower part is about 20%–60%. Horizontal displacement of the isolated model is far larger than that of the nonisolated model, and horizontal displacement will become larger considering FSI effect. These conclusions could provide some references for studies on the isolation system of nuclear island building.

Seismic Analysis and Comparison of Different Base Isolation Systems for a Multi-Storey RC Building with Irregularities in Plan

2012 ◽  
Vol 594-597 ◽  
pp. 1788-1799 ◽  
Author(s):  
Donato Cancellara ◽  
Fabio de Angelis
Keyword(s):  
Base Isolation ◽  
Seismic Analysis ◽  
Cyclic Behavior ◽  
Isolation System ◽  
High Damping Rubber Bearings ◽  
Fixed Base ◽  
Base Isolation System ◽  
High Damping Rubber ◽  
Isolation Systems ◽  
Rubber Bearings

In the present paper the dynamic nonlinear analysis for a 3D base isolated structure is illustrated. A base isolated reinforced concrete building is designed and verified according to the European seismic codes such that the superstructure remains almost completely elastic and the nonlinear elements are localized only in the base isolation system. Nonlinear hysteretic models have been adopted to reproduce the cyclic behavior of the isolators. Two different base isolation systems are considered and their performances are compared for evaluating the behaviour of a base isolated building, highly irregular in plan, in presence of a seismic excitation defined with recorded accelerograms which characterize the bi-directional ground motions. The isolation system has been realized with a combination in parallel of elastomeric bearings and sliding devices. In the first analyzed isolation system we have used the High Damping Rubber Bearings (HDRB) and in the second analyzed isolation system we have used the Lead Rubber Bearings (LRB). Finally a comparative analysis between the base isolated structure with hybrid base isolation systems and the conventional fixed base structure is detailed.

Study on the Seismic Load Coupling Effects Due to Horizontal and Vertical Excitation for the Newly Developed 3-Dimensional Base Isolation System

2005 ◽  
Author(s):  
Tomohiro Ito ◽  
Katsuhisa Fujita ◽  
Takeshi Ohkubo
Keyword(s):  
Friction Force ◽  
Base Isolation ◽  
Seismic Load ◽  
Seismic Excitations ◽  
Coupling Effects ◽  
Isolation System ◽  
Vertical Excitation ◽  
3 Dimensional ◽  
Base Isolation System ◽  
Isolation Systems

Recently, many huge earthquakes occurred in many places, such as Hyogo-ken Nambu earthquake in 1995, Kocaeli earthquake and Chi-Chi earthquake in 1999 and Niigata Chuetsu earthquake in 2004 etc., and huge earthquakes are also considered to occur in near future. Therefore, many horizontal isolation structures have been proposed and constructed. In addition to the horizontal isolation, 3-dimensional isolation systems are under development as well. For these reasons, the authors also have developed a new 3-dimensional base isolation system and evaluated the effectiveness of the system. This isolation system employs sliding pads and laminated rubber bearings for horizontal isolation as some other isolation systems do. Thus, the vibration response of the upper structure depends on the friction force between sliding pads and the floor. In the actual seismic events, these sliding type isolation systems suffer from both horizontal and vertical seismic excitations simultaneously. For these reasons, the friction force in the horizontal direction has two components; one depends on the self weight and the other depends on the vertical seismic response. The latter will change time-dependently. Therefore, it can be said that the coupling effects between the horizontal and vertical seismic excitations become predominant. In this study, the coupling effects of the horizontal and vertical seismic excitations are investigated analytically as for the rocking motion, response displacement and response acceleration for the various seismic wave inputs. The effects of the phase difference between the horizontal and vertical seismic input and the amplitude of the vertical excitation are clarified and the design guide lines for the sliding type base isolation systems exposed to the horizontal and vertical simultaneous seismic excitations are proposed.

Study on the Newly Developed 3-Dimensional Base Isolation System Using a Velocity Reduction Mechanism

2004 ◽  
Author(s):  
Tomohiro Ito ◽  
Katsuhisa Fujita ◽  
Takeshi Ohkubo
Keyword(s):  
Natural Frequency ◽  
High Performance ◽  
Base Isolation ◽  
Structural Parameters ◽  
Active Components ◽  
Isolation System ◽  
Velocity Reduction ◽  
Base Isolation System ◽  
Rocking Motion ◽  
Isolation Systems

Due to the Hyogo-ken Nambu Earthquake in 1995 and the huge earthquakes which are considered to occur in near future, the raise in the seismic design criteria in the horizontal and vertical excitations has been investigated. According to these trends, many base isolation structures have been developed and constructed. However, the most of these structures are limited to the horizontal base isolation. Therefore, the development of the effective 3-dimentional base isolation system becomes more and more important. The conventional 3-dimentional base isolation systems proposed up to now are insufficient in reducing the vertical natural frequency, otherwise are very complex due to facilitation of the active components. In this study, the dynamic characteristics of a high performance 3-dimentional base isolation system newly developed by the authors are reported. This system employs a velocity reduction system using a gear mechanics which can reduce the vertical natural frequency less than 1Hz while that of the conventional system is around 3Hz. And also this employs friction dampers to suppress the large displacement. Further, this system is facilitated with a rocking-suppression system which can effectively suppress the rocking motion inevitable for 3-dimentional base isolation. The response acceleration, displacement and rocking motion are evaluated by numerical simulations in varying the friction force, the predominant frequency of seismic input waves, the eccentricity of the upper structural mass, etc.. As the results, it is shown that the base isolation system developed here has very effective base isolation characteristics and the rocking suppression effects. And the optimization of the structural parameters is also discussed.

Development of a Seismic Isolation System for Commercial Storage Racks

2012 ◽  
Author(s):  
David H. Johnson ◽  
Robert J. Michael ◽  
Michael C. Pollino ◽  
Joseph D. Redovan ◽  
Eric E. Moser ◽  
...  
Keyword(s):  
Structural Damage ◽  
Seismic Isolation ◽  
Structural Engineering ◽  
Base Isolation ◽  
Earthquake Simulation ◽  
Element Analysis ◽  
Isolation System ◽  
Finite Element Analysis Simulation ◽  
Base Isolation System ◽  
Storage Racks

This paper provides an overview of an analysis performed on a new base isolation system developed for seismic isolation of steel pallet storage racks. Pallet storage racks are often found in warehousing for material storage and are designed to store materials on pallets in horizontal rows with multiple levels which are accessed by forklift trucks. The new isolation system provides seismic isolation in the cross-aisle direction by incorporating heavily damped elastomeric bearings (referred to here as seismic mounts) and low-friction bearing plates. The objective of the base isolation system is to reduce horizontal accelerations of the rack to eliminate product shedding and structural damage during a major earthquake without interfering with normal, day-to-day material handling operations. The paper presents a summary of numerical results (transient structural, finite element analysis simulation) comparing storage rack response against actual tests performed on a triaxial shake table in the Structural Engineering and Earthquake Simulation Laboratory (SEESL) at the University at Buffalo (see Filiatrault[1] et al. 2008 for comprehensive test details). The simulation model was then used to determine a set of optimal seismic isolation parameters that satisfy the practical range of rack shelf loads and configurations that can be expected in typical warehouse and store installations.

Improvement of the polyurethane spring isolation device for HV post insulators and its evaluation by fragility curves

2021 ◽  
pp. 875529302098196
Author(s):  
Tansu Gökçe ◽  
Engin Orakdöğen ◽  
Ercan Yüksel
Keyword(s):  
Seismic Isolation ◽  
Base Isolation ◽  
Numerical Models ◽  
Fragility Curves ◽  
Low Cost ◽  
Steel Plates ◽  
Isolation System ◽  
Base Isolation System ◽  
Isolation Device ◽  
Seismic Base Isolation

A novel seismic base isolation system has been developed for high-voltage (HV) porcelain post insulators. The seismic isolation device consists of two steel plates, four polyurethane springs, and a steel rod, which are low-cost components compared to the post insulators. Two alternative designs of the device are experimentally and numerically assessed in this article. A simple and robust numerical model consisting of linear line elements and nonlinear springs was generated, and subsequently validated using the experimental results. Incremental dynamic analyses (IDAs) were then performed to obtain fragility curves. Ten historical earthquake profiles, scaled to intensities between 0.1 and 2.0 g, were then applied to the numerical models. The fragility curves, generated according to the latest version of IEEE-693, demonstrate that the seismic isolation devices are highly effective in diminishing the base moment of the porcelain insulator. It should be noted that relatively large displacements at the top of the pole must be accounted for by ensuring adequate slackness in the flexible conductors.

The Isolation Effect Analysis of Base and Story Isolation System in Vertical Seismic Action

2010 ◽  
Vol 163-167 ◽  
pp. 3893-3898
Author(s):  
Shao Wei Duan ◽  
Xiao Wei Tao ◽  
Hai Kuan Liu
Keyword(s):  
Base Isolation ◽  
Material Point ◽  
Isolation Effect ◽  
Seismic Action ◽  
Isolation System ◽  
Effect Analysis ◽  
Base Isolation System ◽  
Isolation Systems ◽  
Material Points ◽  
Isolation Device

Through establishing single material point model of base isolation system and two material points model of story isolation system in vertical earthquake, the isolation effect of base and story isolation system in vertical earthquake are studied. Results show that two kinds of isolation systems cannot effectively keep apart the vertical seismic action, and the effect is amplified on the contrary, especially the position of isolation layers in story structures affect the amplification effect. Compared with the base and story isolation structures, while using the same isolation device, the former is better than the latter in isolating vertical seismic action.

Performance of Semi-Active Base Isolation Systems under External Explosion

2017 ◽  
Vol 17 (10) ◽  
pp. 1750112 ◽  
Author(s):  
M. Mohebbi ◽  
H. D. Dadkhah
Keyword(s):  
Base Isolation ◽  
Hybrid Control ◽  
Structural Response ◽  
Mr Damper ◽  
Isolation System ◽  
Base Isolation System ◽  
Isolation Systems ◽  
Hybrid Control System ◽  
Blast Loadings ◽  
Active Base

Structures designed against earthquake loads based on using control systems may experience explosions during their lifetime. In this paper, the performance of a hybrid control system composed of a low-damping base isolation and a supplemental magneto-rheological (MR) damper under external explosion has been studied. Base isolation system has the ability of decreasing the maximum structural response under blast loadings by shifting the period of the structure. In addition, MR damper improves the base isolation system performance by controlling the base drift of the structure. Hence, in this paper, the capability of a hybrid base isolation system equipped with an MR damper at the base has been evaluated in reducing the maximum structural response and base drift under external blast loadings. To determine the voltage of the semi-active MR damper, the H2/Linear Quadratic Gaussian (LQG) and clipped-optimal control algorithms have been applied. For numerical simulations, a 10-storey shear frame subjected to blast loadings applied on different floors has been considered and the performance of the hybrid isolation system and MR damper has been studied. The results have proven the effectiveness of the hybrid control system in controlling the maximum response and base drift of the isolated structure against spherical external explosion. Furthermore, comparing the performance of the hybrid passive and semi-active base isolation systems indicates that the semi-active hybrid base isolation system is more effective in reducing the root-mean-square (RMS) value of the base drift. Similarly, it has been found that the semi-active hybrid base isolation system also performs better than the high-damping base isolation system.

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