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 Near-Fault Vertical Ground Motions on Seismic Response of Highway Overcrossings

2008 ◽  
Vol 13 (3) ◽  
pp. 282-290 ◽  
Author(s):  
Sashi K. Kunnath ◽  
Emrah Erduran ◽  
Y. H. Chai ◽  
Mark Yashinsky
Keyword(s):  
Seismic Response ◽  
Ground Motions ◽  
Near Fault ◽  
Vertical Ground Motions ◽  
Vertical Ground

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.

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 Dynamic Response of a Combined Isolation Based Mega-Substructure under Bidirectional Near-Fault Ground Motions

2018 ◽  
Vol 2018 ◽  
pp. 1-15
Author(s):  
Xueyuan Yan ◽  
Weihong Chen ◽  
Shen Shi ◽  
Xuan Wang
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Control Method ◽  
Ground Motions ◽  
Vibration Reduction ◽  
Shaking Table ◽  
Main Body ◽  
Isolation Layer ◽  
Near Fault ◽  
Model Structures

A typical megaframe structure has a high lateral stiffness and is excellent for high-rise structures. However, this high stiffness can lead to poor seismic response of a structure. Seismic isolation technology is a mature and cheap vibration control method that is used for vibration reduction in megaframes. This paper introduces a megaframe structure based on substructure combined isolation. The structure consists of two parts. The main body is a megaframe, and the substructure is the subframe with the combined isolation layer arranged at the bottom of the subframe. The seismic performance of this structure system was evaluated by performing shaking table tests of two megaframe model structures. The responses of the deformation, acceleration, and shear of the structure were measured. The dynamic behaviors of the structure with or without the combined isolation layer when exposed to single and bidirectional near-fault and far-fault ground motions with different peak values were investigated. The results showed that the combined isolation layer can reduce the bidirectional seismic response of the main frame and subframe. The acceleration, base shear, and displacement responses had similar vibration reduction trends for the two model structures, and the structural responses under bidirectional earthquake were generally greater than that under a single directional earthquake. The near-fault pulse effect increased the seismic response of the structure. The increase of the predominant period of ground motion also increased the seismic response of the structure.

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