scholarly journals Influence of Vertical Equivalent Damping Ratio on Seismic Isolation Effectiveness of Nuclear Reactor Building

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4602
Author(s):  
Xiuyun Zhu ◽  
Jianbo Li ◽  
Gao Lin ◽  
Rong Pan
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Nuclear Reactor ◽  
Damping Ratio ◽  
Response Spectra ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Vertical Acceleration ◽  
Equivalent Damping ◽  
Reactor Building

This paper aimed at evaluating the influence of different vertical equivalent damping ratios of a 3-dimensional combined isolation bearing (3D-CIB) as regards seismic response and isolation effectiveness. A comparative study of the seismic response in terms of acceleration floor response spectra (FRS), peak acceleration, displacement response of the nuclear reactor building, and dynamic response of the 3D-CIB was carried out. The results showed that: (1) the horizontal FRS is slightly influenced by the vertical equivalent damping ratio of 3D-CIB, whereas the increase of the vertical equivalent damping ratio has a significant effect on reducing the vertical FRS; (2) the peak vertical acceleration increased with the decrease in the vertical equivalent damping ratios of 3D-CIB and the difference of peak accelerations calculated by the damping ratio of 20 and 25% is within 10%; (3) the increase of the vertical equivalent damping ratio is capable of reducing the horizontal displacement and the rocking effect of the superstructure, and effectively controlling the vertical displacement amplitude; and (4) the vertical equivalent damping ratio of 3D-CIB has a slight effect on its axial force. Consequently, it is demonstrated that the increase of the vertical equivalent damping ratio is advantageous for isolation effectiveness. From the view of displacement control, it is suggested that the 3D-CIB with the vertical an equivalent damping ratio of 15~20% is appropriate and acceptable.

The Contrast of Reduction of Seismic Response in Seismic Specification between China and Japan Caused by Equivalent Damping Ratio

2013 ◽  
Vol 740 ◽  
pp. 721-727
Author(s):  
Wen Jing Nie ◽  
Yu Bai ◽  
Hao Wei Kuang
Keyword(s):  
Seismic Response ◽  
Damping Ratio ◽  
Structural Damping ◽  
Calculation Methods ◽  
Equivalent Damping ◽  
China And Japan

The increase in the structural damping ratio can make the degree of seismic response lower, while the damping ratio causes the seismic response differently in the different national specification. The paper first introduces the principle of equivalent damping ratio of the seismic response calculation methods in seismic specification of China and Japan, then analyzes and compares reduction of seismic response caused by the equivalent damping ratio in seismic specification of China and Japan by calculating data.

Research on the Seismic of a Large Span Roof

2013 ◽  
Vol 838-841 ◽  
pp. 424-427
Author(s):  
Hong Wei Gao ◽  
Yong Yao ◽  
Yun Peng Chu ◽  
Dai Guo Chen
Keyword(s):  
Real Time ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Time Response ◽  
Vertical Acceleration ◽  
Acceleration Response ◽  
Large Span ◽  
Displacement Response ◽  
Horizontal Acceleration

By calculating a large span roof structures, get the intrinsic mode and real-time response of the structural under earthquake. The results showed that, the vertical acceleration response of structure is smaller than the horizontal acceleration response under EL-Centro wave and Tangshan wave. The vertical acceleration response is greater than the horizontal acceleration response under Lanzhou wave. The vertical displacement response of structure is greater than the horizontal displacement response under earthquake. Roof Destructed before the steel skeleton damage.

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.

EFFECTIVENESS OF SEISMIC ISOLATION FOR CABLE-STAYED BRIDGES

2006 ◽  
Vol 06 (01) ◽  
pp. 77-96 ◽  
Author(s):  
B. B. SONEJI ◽  
R. S. JANGID
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Damping Ratio ◽  
Time History ◽  
Time Interval ◽  
Lumped Mass ◽  
Pendulum System ◽  
Isolation Systems ◽  
Rubber Bearings ◽  
Cable Stayed Bridges

This paper investigates the effectiveness of elastomeric and sliding types of isolation systems for the seismic response control of cable-stayed bridges. A simplified two-dimensional lumped-mass finite-element model of the Quincy Bay-view Bridge at Illinois was developed for the investigation. The seismic isolation of cable-stayed bridges is achieved using three different isolators, namely, high damping rubber bearings (HDRB), lead rubber bearings (LRB) and friction pendulum system (FPS). Time history analysis is performed for the bridge with four different earthquake ground motions applied in the longitudinal direction using Newmark's method with linear variation of acceleration over the time interval. The seismic response of the isolated cable-stayed bridge is compared with that of the bridge with no isolation system. The results show that the isolation systems are effective for reducing the absolute acceleration of the deck and the base shear response of the tower. Further, a parametric study is performed by varying the damping ratio, yield strength and friction coefficient of HDRB, LRB and FPS to investigate the influence of these parameters on the seismic response of the bridge. From such a study, optimal values can be found for the isolators for reducing the bridge responses.

Epistemic Uncertainty Quantification of Floor Responses for a Nuclear Reactor Building

2018 ◽  
Author(s):  
Byunghyun Choi ◽  
Akemi Nishida ◽  
Yinsheng Li ◽  
Ken Muramatsu ◽  
Tsuyoshi Takada
Keyword(s):  
Uncertainty Quantification ◽  
Seismic Response ◽  
Power Plants ◽  
Nuclear Reactor ◽  
Epistemic Uncertainty ◽  
Ground Motions ◽  
Response Analysis ◽  
Fukushima Accident ◽  
Modeling Methods ◽  
Reactor Building

After the 2011 Fukushima accident, engineers of nuclear power plants are looking beyond the basic design requirements and ensuring that countermeasures are built in to avert possible nuclear accidents. In seismic probabilistic risk assessment (SPRA), uncertainties can be classified in two ways as aleatory uncertainties or epistemic uncertainties. To improve the reliability of SPRA, the difference in seismic response due to difference of building modelings related to epistemic uncertainty was focused on. Two modeling methods were used for a seismic response analysis: a three-dimensional finite-element model and a conventional sway-rocking stick model. Simulated input ground motions related to aleatory uncertainty were generated for the input waves. Then, the seismic floor response results of the various input ground motions of the two modeling methods were quantified. For the uncertainty quantification related to the different building modelings, a statistical analysis of the floor response results of the nuclear reactor building were further performed. Finally, for the quantification of the uncertainty in the fragility analysis for SPRA, the way to use of these results were discussed.

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.

Study of isolation effectiveness of nuclear reactor building with three-dimensional seismic base isolation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiuyun Zhu ◽  
Rong Pan ◽  
Jianbo Li ◽  
Gao Lin
Keyword(s):  
Seismic Response ◽  
Nuclear Reactor ◽  
Base Isolation ◽  
Three Dimensional ◽  
Seismic Action ◽  
Peak Acceleration ◽  
Content Type ◽  
Vertical Stiffness ◽  
Reactor Building ◽  
Seismic Base Isolation

PurposeIn recent years, three-dimensional (3D) seismic base isolation system has been studied extensively. This paper aims to propose a new 3D combined isolation bearing (3D-CIB) to mitigate the seismic response in both the horizontal and vertical directions.Design/methodology/approachThe new 3D-CIB composed of laminated rubber bearing coupled with combined disk spring bearing (CDSB) was proposed. Comprehensive analysis of constitution and theoretical derivation for 3D-CIB were presented. The advantage of CDSB is that the constitution can be flexibly adjusted according to the requirements of the bearing capacity and vertical stiffness. Hence, four different combinations of CDSB were designed for the 3D-CIB and employed to isolate nuclear reactor building. A comparative study of the seismic response in terms of seismic action, acceleration floor response spectra (FRS), peak acceleration and relative displacement response was carried out.Findings3D-CIB can effectively reduce seismic action, FRS and peak acceleration response of the superstructure in both the horizontal and vertical directions. Overall, the horizontal isolation effectiveness of 3D-CIB was slightly influenced by vertical stiffness. The decrease in the vertical stiffness of the 3D-CIB can reduce the vertical FRS and shift the peak values to a lower frequency. The vertical peak acceleration decreased with a decrease in the vertical stiffness. The superstructure exhibited a rocking effect during the earthquake, and the decrease in the vertical stiffness may increase the rocking of the superstructure.Originality/valueAlthough the advantage of 3D-CIB is that the vertical stiffness can be flexibly adjusted by different constitutions, the vertical stiffness should be designed by properly accounting for the balance between the isolation effectiveness and displacement response. This study of isolation effectiveness can provide the technical basis for the application of 3D-CIB into real engineering of nuclear power plants.

Beneficial performance of a quasi-zero stiffness vibration isolator with generalized geometric nonlinear damping

2020 ◽  
pp. 095745652097238
Author(s):  
Chun Cheng ◽  
Ran Ma ◽  
Yan Hu
Keyword(s):  
Damping Ratio ◽  
Nonlinear Damping ◽  
Vibration Isolator ◽  
Equivalent Damping ◽  
Frequency Responses ◽  
Geometric Nonlinear ◽  
Resonant Region ◽  
Force Transmissibility ◽  
Isolation Performance ◽  
Force And Displacement Transmissibility

Generalized geometric nonlinear damping based on the viscous damper with a non-negative velocity exponent is proposed to improve the isolation performance of a quasi-zero stiffness (QZS) vibration isolator in this paper. Firstly, the generalized geometric nonlinear damping characteristic is derived. Then, the amplitude-frequency responses of the QZS vibration isolator under force and base excitations are obtained, respectively, using the averaging method. Parametric analysis of the force and displacement transmissibility is conducted subsequently. At last, two phenomena are explained from the viewpoint of the equivalent damping ratio. The results show that decreasing the velocity exponent of the horizontal damper is beneficial to reduce the force transmissibility in the resonant region. For the case of base excitation, it is beneficial to select a smaller velocity exponent only when the nonlinear damping ratio is relatively large.

scholarly journals Estimation of Additional Equivalent Damping Ratio of the Damped Structure Based on Energy Dissipation

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Xiuyan Hu ◽  
Qingjun Chen ◽  
Dagen Weng ◽  
Ruifu Zhang ◽  
Xiaosong Ren
Keyword(s):  
Energy Dissipation ◽  
Damping Ratio ◽  
Theoretical Concept ◽  
Estimation Methods ◽  
External Excitation ◽  
Single Degree Of Freedom ◽  
Equivalent Damping ◽  
Seismic Motion ◽  
Practical Engineering ◽  
Energy Dissipation Capacity

In the design of damped structures, the additional equivalent damping ratio (EDR) is an important factor in the evaluation of the energy dissipation effect. However, previous additional EDR estimation methods are complicated and not easy to be applied in practical engineering. Therefore, in this study, a method based on energy dissipation is developed to simplify the estimation of the additional EDR. First, an energy governing equation is established to calculate the structural energy dissipation. By means of dynamic analysis, the ratio of the energy consumed by dampers to that consumed by structural inherent damping is obtained under external excitation. Because the energy dissipation capacity of the installed dampers is reflected by the additional EDR, the abovementioned ratio can be used to estimate the additional EDR of the damped structure. Energy dissipation varies with time, which indicates that the ratio is related to the duration of ground motion. Hence, the energy dissipation during the most intensive period in the entire seismic motion duration is used to calculate the additional EDR. Accordingly, the procedure of the proposed method is presented. The feasibility of this method is verified by using a single-degree-of-freedom system. Then, a benchmark structure with dampers is adopted to illustrate the usefulness of this method in practical engineering applications. In conclusion, the proposed method is not only explicit in the theoretical concept and convenient in application but also reflects the time-varying characteristic of additional EDR, which possesses the value in practical engineering.

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