Exact Solution of the Base-Isolated Structure With Elastomeric-Type Base Isolator

2004 ◽  
Author(s):  
C. S. Tsai ◽  
Tsu-Cheng Chiang ◽  
Bo-Jen Chen
Keyword(s):  
Earthquake Engineering ◽  
Degrees Of Freedom ◽  
Base Isolation ◽  
Time History ◽  
Nonlinear Behavior ◽  
Shaking Table ◽  
Nonlinear Time History Analysis ◽  
Base Isolator ◽  
Isolated Structures ◽  
Base Isolators

Base isolation technologies have been proven to be very efficient in protecting structures from seismic hazards during experimental and theoretical studies. In recent years, there have been more and more engineering applications using base isolators to upgrade the seismic resistibility of structures. Optimum design of the base isolator can lessen the undesirable seismic hazard with the most efficiency. Hence, tracing the nonlinear behavior of the base isolator with good accuracy is important in the engineering profession. In order to predict the nonlinear behavior of base isolated structures precisely, hundreds even thousands of degrees-of-freedom and iterative algorithm are required for nonlinear time history analysis. In view of this, a simple and feasible exact formulation without any iteration has been proposed in this study to calculate the seismic responses of structures with base isolators. Comparison between the experimental results from shaking table tests conducted at National Center for Research on Earthquake Engineering in Taiwan and the analytical results show that the proposed method can accurately simulate the seismic behavior of base isolated structures with elastomeric bearings. Hence, the proposed concept can be used as a reliable tool for engineering professions for preliminary design.

Exact Solution of the Base-Isolated Structure With Sliding Type Base Isolator

2004 ◽  
Author(s):  
C. S. Tsai ◽  
Tsu-Cheng Chiang ◽  
Bo-Jen Chen
Keyword(s):  
Exact Solution ◽  
Seismic Response ◽  
Earthquake Engineering ◽  
Degrees Of Freedom ◽  
Good Accuracy ◽  
Base Isolation ◽  
Time History ◽  
Relative Deformation ◽  
History Analysis ◽  
Base Isolator

The use of base isolation for enhancing the seismic resistibility has been proved as an efficiency way from experimental efforts and theoretical studies. It is usual to insert a flexible device in horizontal direction to permit the most relative deformation at this level. Because of the rigidity of the superstructure is much higher than that of the base isolator underneath the structure, therefore, the behavior of the superstructure can be idealized as a rigid body during earthquakes. In general, hundreds of degrees of freedom and a step-by-step time history analysis are the basic requisitions for calculating the seismic response of a base isolated structure under earthquakes. In order to develop a simple tool which can be easily adopted for calculating the sliding displacement and the shear force of the base isolator, an exact solution for predicting the seismic responses of base isolated structures has been derived in this study. The comparison between the experimental results conducted at National Center for Research on Earthquake Engineering (NCREE) in Taiwan and the analytical results obtained from the exact solution show that the exact formulation derived in this study can predict the seismic response of the base isolated structure with very good accuracy.

Seismic Isolation Retrofit of an Office Building Using Friction Pendulum System

2014 ◽  
Vol 578-579 ◽  
pp. 1361-1365
Author(s):  
Lin Liu ◽  
Xuan Min Li ◽  
Wei Tian
Keyword(s):  
Seismic Isolation ◽  
Base Isolation ◽  
Time History ◽  
Nonlinear Behavior ◽  
Office Building ◽  
Nonlinear Time History Analysis ◽  
Isolation System ◽  
Pendulum System ◽  
Nonlinear Time History ◽  
Friction Pendulum

Friction Pendulum Systems have been used as base isolation systems for both new construction and retrofit around the world. This paper presented its implementation in an office building located in Shanghai. To evaluate its impact on seismic performance of the retrofitted structure, models are needed to capture the intricate nonlinear behavior of both structural components and isolator elements. Nonlinear time history analysis of the building for the original and retrofitted cases was conducted to assess the efficiency of the isolation system at the high earthquake level. The numerical results indicate that the retrofitted structure experiences significantly less damage and less deformation due to the shake isolation and energy dissipation through the isolators.

Dynamic Analysis of the Base Isolator Structure

2010 ◽  
Vol 143-144 ◽  
pp. 832-836
Author(s):  
Ying Li Liu ◽  
Chun Miao Li ◽  
Te Liang Yan
Keyword(s):  
Base Isolation ◽  
New Technology ◽  
Time History ◽  
Social Benefits ◽  
Earthquake Response ◽  
Computing Model ◽  
Base Isolator ◽  
Earthquake Resistant ◽  
Realistic Significance ◽  
Base Isolators

Isolators are included in the new earthquake-resistant standard. This article analyses some questions on base-isolators and presents a non-linear dynamic computing-model for the time-history. A corresponding computer program is also compiled. With the program, the earthquake response of a isolated structure including the displacement, acceleration and the shear force of each floor are calculated and compared with those of the same structure without base-isolation. It has been found that base-isolation has important realistic significance in mitigating earthquake disaster effectively and has enormous economic and social benefits. Therefore it is a kind of extremely popularizing and applying new technology.

Dynamic Characteristics of Base-Isolated Steel Frame under Seismic Ground Motion

2011 ◽  
Vol 255-260 ◽  
pp. 2341-2344
Author(s):  
Mohammad Saeed Masoomi ◽  
Siti Aminah Osman ◽  
Ali Jahanshahi
Keyword(s):  
Ground Motion ◽  
Base Isolation ◽  
Time History ◽  
Steel Structure ◽  
Steel Structures ◽  
Steel Frame ◽  
Nonlinear Time History Analysis ◽  
Seismic Load ◽  
Vector Method ◽  
Seismic Ground Motion

This paper presents the performance of base-isolated steel structures under the seismic load. The main goals of this study are to evaluate the effectiveness of base isolation systems for steel structures against earthquake loads; to verify the modal analysis of steel frame compared with the hand calculation results; and development of a simulating method for base-isolated structure’s responses. Two models were considered in this study, one a steel structure with base-isolated and the other without base-isolated system. The nonlinear time-history analysis of both structures under El Centro 1940 seismic ground motion was used based on finite element method through SAP2000. The mentioned frames were analyzed by Eigenvalue method for linear analysis and Ritz-vector method for nonlinear analysis. Simulation results were presented as time-acceleration graphs for each story, period and frequency of both structures for the first three modes.

Seismic Isolation Devices Based on Sliding between Surfaces with Variable Friction Coefficient

2016 ◽  
Vol 32 (4) ◽  
pp. 2291-2315 ◽  
Author(s):  
Paolo M. Calvi ◽  
Matteo Moratti ◽  
Gian Michele Calvi
Keyword(s):  
Seismic Isolation ◽  
Base Isolation ◽  
Time History ◽  
Absorption Capacity ◽  
Sliding Isolation ◽  
Variable Friction ◽  
Displacement Based ◽  
Nonlinear Time History ◽  
High Level ◽  
Base Isolators

Base isolators are effective tools to favor a high level of building performance under lateral load, providing protection to both structural and nonstructural elements. In this context, this paper discusses the possibility of employing materials with different frictional properties to enhance the response of flat and curved-surface base isolators. Two innovative devices, referred to as “BowTie” and “BowC,” are introduced and discussed in some detail. A series of nonlinear time history analyses are then conducted using a customized computer program and considering a number of case study structures, designed applying a displacement-based approach. The results of the analyses are used to discuss the key differences between variable friction and constant friction sliding isolation devices. It is shown that the newly proposed isolators may represent an improvement on classic base-isolation solutions, in light of their higher energy absorption capacity, which contributes to significantly enhance their performance.

scholarly journals Seismic Fragility Analysis of Multispan Reinforced Concrete Bridges Using Mainshock-Aftershock Sequences

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Yutao Pang ◽  
Li Wu
Keyword(s):  
Reinforced Concrete ◽  
Earthquake Engineering ◽  
Design Method ◽  
Fragility Curves ◽  
Uniform Design ◽  
Time History ◽  
Fragility Analysis ◽  
Nonlinear Time History Analysis ◽  
Aftershock Sequences ◽  
System Fragility

Although the knowledge and technology of performance-based earthquake engineering have rapidly advanced in the past several decades, current seismic design codes simply ignore the effect of aftershocks on the performance of structures. Thus, the present paper investigated the effect of aftershocks on seismic responses of multispan reinforced concrete (RC) bridges using the fragility-based numerical approach. For that purpose, a continuous girder RC bridge class containing 8 bridges was selected based on the statistical analysis of the existing RC bridges in China. 75 recorded mainshock-aftershock seismic sequences from 10 well-known earthquakes were selected in this study. In order to account for the uncertainty of modeling parameters, uniform design method was applied as the sampling method for generating the samples for fragility analysis. Fragility curves were then developed using nonlinear time-history analysis in terms of the peak curvature of pier column and displacement of bearings. Finally, the system fragility curves were derived by implementing Monte Carlo simulation on multinormal distribution of two components. From the results of this investigation, it was found that, for the RC continuous bridges, the influence of aftershocks can be harmful to both bridge components and system, which increases both the component fragility of the displacement of bearings and seismic curvature of pier sections and system fragility.

Shaking Table Test for Base-Isolated Nuclear Island Structure Model

2017 ◽  
Author(s):  
Yang Jie ◽  
Li ShaoPing ◽  
Yuan Fang ◽  
Xia ZuFeng ◽  
Huang XiaoLin
Keyword(s):  
Shaking Table Test ◽  
Three Dimensional ◽  
Time History ◽  
Response Spectra ◽  
Shaking Table ◽  
Nonlinear Time History Analysis ◽  
Earthquake Simulation ◽  
Maximum Displacement ◽  
Island Structure ◽  
Reduced Scale

In this paper, the base-isolated design of Nuclear Island structure will be introduced, including the general requirement and the goal of the base-isolated design. Integrated assessment has been performed for the base-isolated design of Nuclear Island structure in the earthquake 0.6g. A series of nonlinear time-history analysis were performed to predict the maximum displacement and acceleration of the isolation layer, the maximum stress of the isolation units, and the floor response spectra of each story of the superstructure in the earthquake 0.6g, considering the realistic mechanical properties and the layout of the isolators. In order to provide realistic data to validate the numerical method, a reduced-scale earthquake simulation of base-isolated nuclear structure on a shaking table was carried out. The study was primarily focused on the response of superstructure and the isolation unit. The dynamic characteristic was examined, together with the vibration acceleration and displacement under different levels of seismic wave. The test results of a reduced-scale nuclear island model previously tested on a shaking table were compared with three-dimensional finite element simulation results. The results of this study provide the technical basis for the base-isolated design of Nuclear Island structure.

Analysis and Experiment on the Effect of Seismic Protection of Buildings by High Damping Rubber Bearings

2004 ◽  
Author(s):  
Jun-Ping Pu ◽  
C. S. Tsai ◽  
Jian-Fa Huang ◽  
Bo-Jen Chen ◽  
Yao-Min Fang
Keyword(s):  
Earthquake Engineering ◽  
Base Isolation ◽  
Steel Structure ◽  
Shaking Table ◽  
Natural Period ◽  
Rubber Bearing ◽  
High Damping Rubber Bearings ◽  
High Damping Rubber Bearing ◽  
High Damping Rubber ◽  
Rubber Bearings

In recent years, many studies on base isolation strategies and devices have been developed and applied in U. S. A., Europe, Japan, and New Zealand. The high damping rubber bearing belongs to one kind of the earthquake-proof ideas of base isolation technologies. The installation of high damping rubber bearings can lengthen the natural period of a building and simultaneously reduce the earthquake-induced energy trying to impart to the building. The objective of this paper is to investigate the base isolation effect of high damping rubber bearings. The uniaxial, biaxial, and triaxial shaking table tests were performed to study the seismic behavior of a 0.4-scale three-story isolated steel structure in the National Center for Research on Earthquake Engineering in Taiwan. The experimental and analytical results show that the nonlinear mechanical characteristics of the high damping rubber bearings can be reasonably simulated.

INFLUENCE OF HIGH INITIAL ISOLATOR STIFFNESS ON THE SEISMIC RESPONSE OF A BASE-ISOLATED BENCHMARK BUILDING

2011 ◽  
Vol 11 (06) ◽  
pp. 1201-1228 ◽  
Author(s):  
AJAY SHARMA ◽  
R. S. JANGID
Keyword(s):  
Degrees Of Freedom ◽  
Base Isolation ◽  
Near Field ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Time History ◽  
Base Shear ◽  
Isolation System ◽  
Base Displacement ◽  
Floor Acceleration

The influence of high initial isolator stiffness on the response of a base-isolated benchmark building is investigated. The base-isolated building is modeled as a three-dimensional linear-elastic structure having three degrees-of-freedom at each floor level. The time-history analysis of this building is carried out by solving the governing equations of motion using Newmark-beta method along with an iterative predictor–corrector approach. The force–deformation behavior of the isolation system is modeled by a bilinear law, which can be effectively used to model all isolation systems in practice. Three near-field earthquakes with bidirectional ground motions are considered. Structural response parameters such as absolute top floor acceleration, base shear, and base displacement are chosen for investigating the effects of high initial isolator stiffness. It was observed that the high initial isolator stiffness of the isolation system excites the higher modes in the base-isolated building and increases the top floor acceleration. Such a phenomenon can be detrimental to the sensitive instruments placed in the isolated structure. On the other hand, both the base displacement and base shear reduce marginally due to increase in the initial isolator stiffness. Further, the influences of high initial isolator stiffness are found to dependent on the period and characteristic strengths of the base isolation system.

scholarly journals Isolating system using U Shaped steel damper

2021 ◽  
Vol 309 ◽  
pp. 01136
Author(s):  
Siripuram Vamshisheela ◽  
Atulkumar Manchalwar
Keyword(s):  
Base Isolation ◽  
Ground Motions ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Base Shear ◽  
Energy Device ◽  
History Analysis ◽  
Structural Responses ◽  
Nonlinear Time History ◽  
Story Building

In this work the performance of U-Shaped Steel Isolator is evaluated for a 5-story building subjected to seismic and blast vibrations. The structure is analysed using SAP 2000 software and a nonlinear time history analysis is carried out. The effectiveness of using base isolation is studied by comparing the structural responses of the building with isolator and without isolator and noticeable difference was observed. As the U-Shaped isolator absorbs the energy in all directions, it effectively controls the structural responses. In this study, the building is subjected to four different seismic and four different blast induced ground motions. It was observed that by the use of supplementary energy device there is reduction in top story acceleration, base shear and less deformation in the structure. This study concludes that the use of isolator has been effective in minimizing structural responses.

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