Vertical Vibration Control of Series Isolation System under Near-Fault Earthquake

2014 ◽  
Vol 638-640 ◽  
pp. 1952-1955
Author(s):  
Q. Rong ◽  
Yan Sheng ◽  
Shi Xin Liu
Keyword(s):  
Seismic Waves ◽  
Damping Ratio ◽  
Vertical Vibration ◽  
Isolation Effect ◽  
Earthquake Intensity ◽  
Isolation System ◽  
Vertical Stiffness ◽  
Isolation Layer ◽  
Near Fault ◽  
Composite Disk

Series isolation system consists of rubber isolation bearings and composite disk springs, determination method of vertical stiffness and vertical damping of isolation layer is given. Entering the near-fault vertical seismic waves, the affect of isolation layer parameters and earthquake intensity on the isolation effect is studied. Studies have shown that the vertical isolation effect increases with the increase of vertical damping ratio. When the damping ratio reaches a certain value, the isolated effect leveles off. When calculating model is adopted as the hierarchical model, vertical isolation effect has nothing to do with the increases of earthquake intensity.

Investigations on a mega–sub isolation system under near-fault ground motions

2021 ◽  
pp. 136943322110262
Author(s):  
Xiangxiu Li ◽  
Ping Tan ◽  
Aiwen Liu ◽  
Xiaojun Li
Keyword(s):  
Failure Mechanism ◽  
Ground Motion ◽  
Failure Probability ◽  
Structural Parameters ◽  
Ground Motions ◽  
Damping Ratio ◽  
Correlation Coefficients ◽  
Isolation System ◽  
Isolation Layer ◽  
Near Fault

The failure mechanism of the mega–sub isolation system under near-fault ground motions is studied in this article. 90 suites of near-fault ground motions collected from 23 earthquakes are adopted to investigate the ground motion intensity indices applicable for the mega–sub isolation system. Then, the sensitivities of the stochastic responses to the structural parameters are analyzed to determine the representative random structural parameters. Furthermore, considering the uncertainties of ground motion characteristics and structural parameters, the seismic fragility is analyzed by the response surface method in order to obtain the failure mechanism of this system under near-fault ground motions. Results show that different intensity indices have various correlation coefficients with the peak responses of the mega–sub isolation system. The correlations of acceleration-related intensity indices are the worst, whereas the correlations of displacement-related intensity indices show high linearity. The sensitivities of the structural responses are weaker to the sub-structure story stiffness but more sensitive to the sub-structure story mass and the stiffness and damping ratio of the isolation layer. The failure probability of the sub-structure is higher than that of the mega-structure under near-fault ground motion. While in the collapse state, the failure probability of the isolation layer is greater than that of the sub-structure.

scholarly journals Horizontal-Vertical-Rocking Coupled Response Analysis of Vertical Seismic Isolated Structure under Near-Fault Earthquakes

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Dewen Liu ◽  
Yafei Zhang ◽  
Sitong Fang ◽  
Yang Liu
Keyword(s):  
Seismic Isolation ◽  
Damping Ratio ◽  
Vertical Displacement ◽  
Response Analysis ◽  
Isolation System ◽  
Vertical Stiffness ◽  
Near Fault ◽  
Isolated Structures ◽  
Nonlinear Dynamic Analyses ◽  
Near Fault Earthquakes

For vertical isolated structures with excessive vertical eccentricity for mass and vertical stiffness, horizontal-vertical-rocking response needs to be better understood for vertical isolated structures located in near-fault areas, where long-period velocity pulse can be produced. In this study, a seismic isolation system including quasizero stiffness (QZS) and vertical damper (VD) is used to control near-fault (NF) vertical earthquakes. The responses of horizontal-vertical-rocking coupling base-isolated structure including quasizero stiffness (QZS) and vertical damper (VD) subjected to NF horizontal and vertical ground motions are investigated. Nonlinear dynamic analyses are conducted to study the effects of essential parameters such as isolation system eccentricity, static equilibrium position, vertical isolation period, and vertical damping ratio on seismic responses of vertical isolated structure. It is found that increasing vertical period and damping ratio causes the vertical isolated structures to behave well in reducing rocking responses of structure. The effect of horizontal-vertical-rocking coupling on vertical seismic isolation efficiency is insignificant. The vertical seismic isolation remains effective as compared to the system supported on rubber bearings. The vertical damping can significantly control the vertical displacement and rocking moment.

scholarly journals A Study on Seismic Isolation of Shield Tunnel Using Quasi-Static Finite Element Method

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Can Li ◽  
Weizhong Chen ◽  
Wusheng Zhao ◽  
Takeyasu Suzuki ◽  
Yoshihiro Shishikura
Keyword(s):  
Finite Element ◽  
Shear Modulus ◽  
Seismic Isolation ◽  
Transverse Direction ◽  
Longitudinal Direction ◽  
Isolation Effect ◽  
Poisson's Ratio ◽  
Shield Tunnel ◽  
Isolation System ◽  
Isolation Layer

Using a quasi-static method based on an axisymmetric finite element model for seismic response analysis of seismically isolated tunnels, the seismic isolation effect of the isolation layer is studied, and the seismic isolation mechanism of the isolation layer is clarified. The results show that, along the longitudinal direction of the tunnel, the seismic isolation effect is mainly affected by the shear modulus of the isolation material. The smaller the shear modulus is, the more evident the seismic isolation effect is. This is due to the tunnel being isolated from deformation of its peripheral ground through shear deformation of the isolation layer. However, along the transverse direction of the tunnel, the seismic isolation effect is mainly affected by the shear modulus and Poisson’s ratio of the isolation material. When Poisson’s ratio is close to 0.5, a seismic isolation effect is not evident because the tunnel cannot be isolated from deformation of its peripheral ground through compression deformation of the isolation layer. Finally, a seismic isolation system comprising a shield tunnel in which flexible segments are arranged at both ends of an isolation layer is proposed, and it is proved that the seismic isolation system has significant seismic isolation effects both on the longitudinal direction and on the transverse direction.

scholarly journals Analytical and Experimental Overview of Fiber Reinforced Elastomeric Isolator

2021 ◽  
Vol 9 (VII) ◽  
pp. 3906-3911
Author(s):  
Afroz Qureshi
Keyword(s):  
Seismic Isolation ◽  
Seismic Waves ◽  
Base Isolation ◽  
Low Cost ◽  
Fiber Reinforced ◽  
Effective Response ◽  
Isolation System ◽  
Vertical Stiffness ◽  
Base Isolation System ◽  
Fiber Reinforced Elastomeric Isolator

There has been many researches in order to further improve the Base Isolation system by trying various combinations and alternative materials. In that fiber reinforced isometric isolators are emerged as a viable solution, because for the low cost and effective response to seismic waves as compared to the conventional isolators. Studies further shows that it provides high vertical stiffness and low horizontal stiffness, also having effective damping over the conventional one. Developing countries who doesn’t have proper seismic protection solutions have found this convenient as they are comparatively less in cost and doesn’t require complex installation. Studies also shows Un-bonded FREI has lower horizontal stiffness and considerably lower stress demand on rubber material as compared to the B-FREI and hence significantly higher seismic isolation efficiency.

scholarly journals Dynamic Behavior of a Suspended Steel Space Frame-Glass Composite Floor

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zhihao Wang ◽  
Xin Qi ◽  
Youkun Huang ◽  
Buqiao Fan ◽  
Xiaoke Li
Keyword(s):  
Dynamic Characteristics ◽  
Damping Ratio ◽  
Dynamic Performance ◽  
Vertical Vibration ◽  
Ambient Vibration ◽  
Fe Model ◽  
Glass Composite ◽  
Space Frame ◽  
Vertical Stiffness ◽  
Steel Space Frame

This study investigates the dynamic performance of a large-span suspended steel space frame-glass composite floor (SSSF-GCF). Both the ambient vibration and the human-induced vibration of the floor were experimentally measured to identify vertical dynamic characteristics and evaluate vibration serviceability of the floor. Although vertical dynamic characteristics of the floor based on the global simplified finite element (FE) model of the structure agree well with those identified via experimental modal analysis, the global simplified FE model significantly underestimates vertical vibration amplitudes of the floor due to the coupled effect between two layers. Accordingly, an equivalent local FE model of the floor system was proposed and updated via adjusting the vertical stiffness of the interstory hanging pillars. It is shown that the equivalent local FE model can well predict both the dynamic characteristics and human-induced vibration response of the floor. Finally, the effect of the damping ratio on the acceleration response of the floor was numerically demonstrated with the verified local FE model.

Displacement mitigation–oriented design and mechanism for inerter-based isolation system

2020 ◽  
pp. 107754632095166 ◽  
Author(s):  
Zhipeng Zhao ◽  
Ruifu Zhang ◽  
Nicholas E Wierschem ◽  
Yiyao Jiang ◽  
Chao Pan
Keyword(s):  
Damping Ratio ◽  
Dynamic Performance ◽  
Fundamental Equation ◽  
Design Procedure ◽  
Target Displacement ◽  
Design Strategies ◽  
Isolation System ◽  
Demand Equation ◽  
Isolation Layer ◽  
Displacement Demand

The inerter-based isolation system, which comprises an inerter, a dashpot, and a spring, has been shown to be effective for improving the dynamic performance of isolated structures. However, the underlying theoretical basis of its vibration control mechanism has not been studied for superstructures with inerter-based isolation system; in particular, the functionality of the inerter has not been explicitly demonstrated. In this study, the displacement mitigation mechanism is established by deriving a fundamental equation, designated as the displacement demand equation. The mechanism is explained by clarifying the functionality of the inerter-based isolation system to determine the theoretical relationship between the displacements of the superstructure and isolation layer. A nominal displacement demand ratio is defined to evaluate the overall displacement demand of the structure–inerter-based isolation system, by considering the contribution of the inerter-based isolation system. Following the displacement mitigation mechanism, design strategies are developed for inerter-based isolation system, where the isolation frequency ratio can be directly determined once the target displacement performance of the entire structure–inerter-based isolation system is prespecified. In addition, the inertance-mass ratio and damping ratio of the inerter-based isolation system can be obtained according to the target demand of the superstructure displacement. Finally, a series of examples are used to verify the derived displacement demand equation and proposed design strategy. In this study, the displacement mitigation mechanism yields an effective design method that is suitable for the inerter-based isolation system and has a clear physical basis. Through the proposed displacement mitigation–oriented optimal strategy, a target displacement demand for a structure can be satisfied directly, which also provides an optimized displacement performance for the isolation layer. The displacement mitigation mechanism and equation are practical for the simplification of the design procedure and help to reveal the advantageous features of the inerter-based isolation system.

scholarly journals Seismic Response Analysis of an Isolated Structure with QZS under Near-Fault Vertical Earthquakes

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Dewen Liu ◽  
Yang Liu ◽  
Dongfa Sheng ◽  
Wenyuan Liao
Keyword(s):  
Bearing Capacity ◽  
Seismic Response ◽  
Large Deformation ◽  
Seismic Isolation ◽  
Ground Motions ◽  
Damping Ratio ◽  
Isolation System ◽  
Near Fault ◽  
Vertical Ground Motions ◽  
Vertical Ground

Seismic isolation devices are usually designed to protect structures from the strong horizontal component of earthquake ground shaking. However, the effect of near-fault (NF) vertical ground motions on seismic responses of buildings has become an important consideration due to the observed building damage caused by vertical excitation. As the structure needs to maintain its load bearing capacity, using the horizontal isolation strategy in vertical seismic isolation will lead to the problem of larger static displacement. In particular, the bearings may generate large deformation responses of isolators for NF vertical ground motions. A seismic isolation system including quasi-zero stiffness (QZS) and vertical damper (VD) is used to control NF vertical earthquakes. The characteristics of vertical seismic isolated structures incorporating QZS and VD are presented. The formula for the maximum bearing capacity of QZS isolation considering the stiffness of vertical spring components is obtained by theoretical derivation. From the static analysis, it is found that the static capacity of the QZS isolation system with vertical seismic isolation components increases when the configurative parameter reduces. Seismic response analyses of the seismic isolated structure model with QZS and VD subjected to NF vertical earthquakes are conducted. The results show that seismic responses of the structure can be controlled by setting the appropriate static equilibrium position, vertical isolation period, and vertical damping ratio. Adding a damping ratio is effective in controlling the vertical large deformation of the isolator.

Effect of Supplemental Damping on the Seismic Performance of Triple Pendulum Bearing Isolators under Near-Fault Ground Motions

2016 ◽  
Vol 845 ◽  
pp. 240-245
Author(s):  
Sima Rezaei ◽  
Gholamreza Ghodrati Amiri
Keyword(s):  
Seismic Isolation ◽  
Ground Motions ◽  
Damping Ratio ◽  
Three Dimensional ◽  
Time History ◽  
Period Range ◽  
Natural Period ◽  
Isolation System ◽  
Near Fault ◽  
Triple Pendulum

The isolating system absorbs part of the earthquake energy before transferring it to the structure, by shifting the natural period of the isolated structure. This period shift results in a reduction in the inertial forces. It is clear that the effects of near-fault (NF) ground motions with large velocity pulses can bring the seismic isolation devices to critical working conditions. In this study, two three-dimensional RC buildings with the heights of 9.0m and 21.0m which are supported by Triple Friction Pendulum Bearing (TFPB) isolators are idealized. Various TFPB configurations are selected for isolation systems. There are also viscous dampers to limit the excess deformation of isolators. Nonlinear time history analyses were performed by using OpenSees to study the influence of supplemental dampers on structural responses such as isolator displacements and maximum drifts under ten near-fault ground motion records. The results show noticeable reduction in isolator displacement when using dampers. However, maximum drift rises considerablely. Moreover by increasing the period range or reducing the damping ratio of isolation system, maximum driftreduces but the displacement of isolator increases.

Isolation Performance of Intelligent Seismic Isolation System Using Air Bearing

2009 ◽  
Author(s):  
Satoshi Fujita ◽  
Keisuke Minagawa ◽  
Mitsuru Miyazaki ◽  
Go Tanaka ◽  
Toshio Omi ◽  
...  
Keyword(s):  
Seismic Isolation ◽  
Seismic Waves ◽  
Three Dimensional ◽  
Vertical Motion ◽  
Air Bearings ◽  
Natural Period ◽  
Isolation System ◽  
Vertical Excitation ◽  
Long Period ◽  
Isolation Performance

This paper describes three-dimensional isolation performance of seismic isolation system using air bearings. Long period seismic waves having predominant period of from a few seconds to a few ten seconds have recently been observed in various earthquakes. Also resonances of high-rise buildings and sloshing of petroleum tanks in consequence of long period seismic waves have been reported. Therefore the isolation systems having very long natural period or no natural period are required. In a previous paper [1], we proposed an isolation system having no natural period by using air bearings. Additionally we have already reported an introduction of the system, and have investigated horizontal motion during earthquake in the previous paper. It was confirmed by horizontal vibration experiment and simulation in the previous paper that the proposed system had good performance of isolation. However vertical motion should be investigated, because vertical motion varies horizontal frictional force. Therefore this paper describes investigation regarding vertical motion of the proposed system by experiment. At first, a vertical excitation test of the system is carried out so as to investigate vertical dynamic property. Then a three-dimensional vibration test using seismic waves is carried out so as to investigate performance of isolation against three-dimensional seismic waves.

scholarly journals Influence of Elastomeric Bearings in Tension on the Seismic Performance of Base-Isolated r.c. Buildings

2020 ◽  
Vol 11 (1) ◽  
pp. 82
Author(s):  
Fabio Mazza ◽  
Mirko Mazza
Keyword(s):  
Base Isolation ◽  
Nonlinear Models ◽  
Vertical Component ◽  
Computer Code ◽  
Nonlinear Phenomena ◽  
Isolation System ◽  
Elastomeric Bearings ◽  
Near Fault ◽  
Base Isolation System ◽  
Near Fault Earthquakes

Elastomeric bearings are commonly used in base-isolation systems to protect the structures from earthquake damages. Their design is usually developed by using nonlinear models where only the effects of shear and compressive loads are considered, but uncertainties still remain about consequences of the tensile loads produced by severe earthquakes like the near-fault ones. The present work aims to highlight the relapses of tension on the response of bearings and superstructure. To this end, three-, seven- and ten-storey r.c. framed buildings are designed in line with the current Italian seismic code, with a base-isolation system constituted of High-Damping-Rubber Bearings (HDRBs) designed for three values of the ratio between the vertical and horizontal stiffnesses. Experimental and analytical results available in literature are used to propose a unified nonlinear model of the HDRBs, including cavitation and post-cavitation of the elastomer. Nonlinear incremental dynamic analyses of the test structures are carried out using a homemade computer code, where other models of HDRBs considering only some nonlinear phenomena are implemented. Near-fault earthquakes with comparable horizontal and vertical components, prevailing horizontal component and prevailing vertical component are considered as seismic input. Numerical results highlight that a precautionary estimation of response parameters of the HDRBs is attained referring to the proposed model, while its effects on the nonlinear response of the superstructure are less conservative.

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