Effects of Isolation Damping on Stochastic Response of Structures with Nonlinear Base Isolators

1998 ◽  
Vol 14 (1) ◽  
pp. 95-114 ◽  
Author(s):  
R. S. Jangid ◽  
P. Banerji
Keyword(s):  
Sliding Friction ◽  
Base Isolation ◽  
Equivalent Linearization ◽  
Earthquake Intensity ◽  
Analytical Expression ◽  
Time Period ◽  
Stiffness Properties ◽  
Fixed Base ◽  
Optimum Material ◽  
Design Earthquake

Optimum isolator damping required to minimize absolute acceleration responses to stochastic ground motions in buildings with non-linear resilient-friction base isolation (R-FBI) devices is studied. Using a stochastic equivalent linearization technique, an analytical expression is developed for estimating optimum material damping values in an R-FBI system for a rigid superstructure. This optimum damping value depends on the effective time period and friction coefficient of the R-FBI system and the design earthquake intensity. The fixed base structural time period, damping, and the number of stories also affect the optimum isolator damping values, if the superstructure is flexible. However, the analytical expression mentioned above provides an upper-bound optimum isolator damping value for any superstructure with an R-FBI system subjected to a given earthquake intensity. Comparison of optimum damping values for a linear isolator and the R-FBI system, with identical lateral stiffness properties, illustrates the beneficial effect of sliding friction in reducing the optimum damping in the latter type of isolator, for a given earthquake intensity.

Analysis and Demonstrative Application of a Base Isolation/Supplemental Damping Technology

2008 ◽  
Vol 24 (3) ◽  
pp. 775-793 ◽  
Author(s):  
Stefano Sorace ◽  
Gloria Terenzi
Keyword(s):  
Base Isolation ◽  
Numerical Models ◽  
Ground Acceleration ◽  
Fixed Base ◽  
Supplemental Damping ◽  
And Performance ◽  
High Damping Rubber ◽  
Design Earthquake ◽  
Rubber Bearings ◽  
The Cost

As a concluding step of several studies on a special base isolation/supplemental damping system, where pressurized fluid viscous spring-dampers are coupled to steel-Teflon sliders, the system was applied for the first time to a demonstrative strategic building in Italy. A final experimental campaign was developed to assess the interference of the dissipative actions of the two component devices. The campaign confirmed the linear additive combination implicitly assumed in relevant numerical models. The design and performance evaluation analyses performed on the building showed that maximum base displacements were only just below 45 mm, for the basic design earthquake level. As a result, very simple joints for all the facilities were used. For the same earthquake level, reduction factors of 2.48 and 2.12 on the superstructure response accelerations were obtained for the two main directions in plan as compared to peak ground acceleration. Low base displacement values, and a totally elastic superstructure response also emerged for the maximum earthquake level considered, as well as for the most demanding Italian historical near-fault ground motions introduced as inputs in the final verification analyses. The cost of the building structure resulted to be around 10% lower than the cost of a fixed-base traditional design, as well as of a base isolated structure incorporating high damping rubber bearings.

scholarly journals Seismic Performance Evaluation of Double-Skin Semi-Base-Isolated Building Using Incremental Dynamic Analysis

2018 ◽  
Vol 2018 ◽  
pp. 1-19 ◽  
Author(s):  
Mohammad Parsaeimaram ◽  
Congqi Fang ◽  
Xianqi Luo ◽  
Chandan Shakya
Keyword(s):  
Inner Core ◽  
Base Isolation ◽  
Shear Walls ◽  
Dynamic Responses ◽  
Coupling Beams ◽  
Skin Structure ◽  
Seismic Performance Evaluation ◽  
Time Period ◽  
Fixed Base ◽  
Double Skin

Base isolation is a widely accepted earthquake damage prevention technique. This method decouples the superstructure from the base by putting a flexible layer under each column, thereby elongating the time period of structures. Semi-base isolation (SBI) in double-skin structures is an effective technique to reduce the dynamic responses of structures due to earthquake motions, by utilizing the isolation devices in part of it instead of the entire base. This study presents a double-skin structure consisting of outer fixed base frames with shear walls that have been detached from the inner core with a minor gap. The inner core of the structure has been dissociated from the base using the elastomeric bearings. Seismic response of 10-story double-skin structure with inner isolated core was compared to that of inner fixed base core to consider the yielding and collapse probability of the structure using the incremental dynamic analyses (IDA). The results showed that the time period in SBI buildings can be adjusted with the use of coupling beams between the inner and outer frames. Also, the time period and interstory drift ratio are both reduced as more floors are given coupling beams. However, these coupling beams are the most effective at the topmost floors.

Dynamic Nonlinear Analysis of an Hybrid Base Isolation System with Viscous Dampers and Friction Sliders in Parallel

2012 ◽  
Vol 234 ◽  
pp. 96-101 ◽  
Author(s):  
Donato Cancellara ◽  
Fabio de Angelis
Keyword(s):  
Nonlinear Analysis ◽  
Base Isolation ◽  
Three Dimensional ◽  
Time History ◽  
Seismic Action ◽  
Viscous Dampers ◽  
Isolation System ◽  
Fixed Base ◽  
Base Isolation System ◽  
Dynamic Nonlinear Analysis

In the present work we have analyzed a particular base isolation system for the seismic protection of a multi-storey reinforced concrete (RC) building. The viscous dampers and friction sliders are the devices adopted in parallel for realizing the base isolation system. The base isolation structure has been designed and verified according to European seismic code EC8 and by considering for the friction sliders the influence of the sliding velocity on the value of the friction coefficient. A dynamic nonlinear analysis for a three-dimensional base isolated structure has been performed. Recorded accelerograms for bi-directional ground motions have been used which comply with the requirements imposed by EC8 for the representation of a seismic action in a time history analysis. In this paper a comparative analysis is presented between the base isolated structure with the described hybrid base isolation system and the traditional fixed base structure.

Pushover Analysis of Base Isolated RC Frame Buildings With Masonry Infills

2019 ◽  
Vol 10 (2) ◽  
pp. 18-31
Author(s):  
Radhikesh Prasad Nanda ◽  
Subhrasmita Majumder
Keyword(s):  
Base Isolation ◽  
Plastic Hinge ◽  
Pushover Analysis ◽  
Base Shear ◽  
Infilled Frame ◽  
Masonry Infills ◽  
Time Period ◽  
Frame Buildings ◽  
Story Drift ◽  
Rc Frame Buildings

In the present article, the performance of base-isolated infilled frames is studied analytically. The seismic performances of four RC buildings, namely RC bare frame without isolator, RC bare frame with isolator, RC infilled frame without isolator, and RC infilled frame with isolator are analysed. The results show a decrease in base shear value and increase in time period due to base isolated buildings, while these parameters are reversely affected due to infills. The decrease in story drift for the base isolated buildings is in phase while considering infill. Also, it can be inferred that plastic hinge formation is greatly affected by the introduction of masonry infill. Hence, relying on base isolation without considering infills may underestimate the seismic performance.

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.

scholarly journals Innovative Structural Solutions for Prefab Reinforced Concrete Hall-Type Buildings

2019 ◽  
Vol 13 (1) ◽  
pp. 149-163 ◽  
Author(s):  
Stefano Sorace ◽  
Gloria Terenzi
Keyword(s):  
Reinforced Concrete ◽  
Seismic Isolation ◽  
Base Isolation ◽  
Seismic Protection ◽  
Isolation System ◽  
Fluid Viscous Dampers ◽  
Protection Strategies ◽  
Additional Costs ◽  
Design Earthquake ◽  
Bracing System

Background:The anti-seismic design of prefab reinforced concrete buildings is usually carried out with a conventional ductility-based approach. This implies a remarkable plastic demand on columns, as well as damages to the connections of structural and non-structural members, for seismic events with comparable intensity to the basic design earthquake normative level.Objective:In view of this, a study was developed and aimed at extending to the field of new prefab reinforced concrete structures the application of advanced seismic protection strategies, capable of guaranteeing undamaged response up to the maximum considered earthquake normative level.Method:A benchmark building was designed as demonstrative case study for this purpose, in the three following hypotheses: (a) according to a traditional ductility-based approach; (b) by incorporating dissipative bracings, equipped with fluid viscous dampers; (c) by placing a seismic isolation system at the base, composed of a set of double curved surface sliders.Results:The results of the verification analyses show that the targeted performance for the design solutions b) and c) is obtained with sizes of columns and plinths notably smaller than those for the conventional design. This allows compensating the additional cost related to the incorporation of the protective devices, for the dissipative bracing system, and limiting additional costs below 25%, for the base isolation solution. At the same time, a supplemental benefit of the latter is represented by greater protection of contents and plants, as they are fully supported by the seismically isolated ground floor.Conclusion:The study highlights the advantages offered by the two advanced seismic protection technologies in an unusual field of application, guaranteeing an enhanced performance of structural and non-structural elements, as well as reduced member sizes, as compared to the traditional ductility-based design.

scholarly journals Dissipation of Hysteretic Energy in Base Isolated Structure

1996 ◽  
Vol 3 (5) ◽  
pp. 353-359 ◽  
Author(s):  
R.S. Jangid ◽  
T.K. Datta
Keyword(s):  
Base Isolation ◽  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Earthquake Ground Motion ◽  
Hysteretic Energy ◽  
Isolation Frequency ◽  
Time Period ◽  
Base Isolator ◽  
Energy Dissipated ◽  
Mass Level

Dissipation of hysteretic energy in the isolator of the base isolated structure under seismic excitation is investigated. The hysteretic force-deformation characteristics of the base isolator is specified by a nonlinear differential equation. The parameters of the equation can be adjusted to obtain various types of hysteretic models of the isolator including the elastoplastic type. The variation of hysteretic energy dissipated in the isolators is obtained for both harmonic and El-Centro 1940 earthquake ground motion for a set of important parameters. They include time period of superstructure, ratio of superstructure mass to base mass, level of yield strength of the isolator, post- to preyielding stiffness ratio, and the ratio of harmonic excitation frequency to base isolation frequency. It is shown that the dissipation of hysteretic energy in the isolator is significantly influenced by the above parameters.

scholarly journals Shaking Table Tests on Earthquake Response Characterization of a Complex Museum Isolated Structure in High Intensity Area

2016 ◽  
Vol 2016 ◽  
pp. 1-23 ◽  
Author(s):  
Wenguang Liu ◽  
Chuan Qin ◽  
Yang Liu ◽  
Wenfu He ◽  
Qiaorong Yang
Keyword(s):  
Structural Model ◽  
Base Isolation ◽  
Shaking Table ◽  
Isolation Effect ◽  
Structural Safety ◽  
Functional Requirements ◽  
Shaking Table Tests ◽  
Earthquake Intensity ◽  
Long Span ◽  
Museum Design

Owing to special functional requirements of museum, such as great space and story height for exhibitions, large floor slab openings in plan and long span truss in elevation are becoming increasingly considered in museum design, which leads to challenges to structural safety. The aseismic performance of an isolated museum structure in high earthquake intensity regions was thus studied because of its complexity and irregularity. In order to observe the seismic characteristics and verify isolation effect, shaking table tests of a 1/30-scale structural model with and without base isolation bearings have been carried out under minor, moderate, and major earthquakes. The experimental results show that isolated structure dynamic characteristics and isolation effect are stable and storey peak acceleration responses of superstructure are less than that of fixed structure. Storey drifts of isolated structure meet required limits stipulated in Chinese design code and torsion responses of the bearings are not remarkable. It is suggested that seismic performances of complex museum structures have been effectively improved with isolation in use.

Seismic Isolation of Buildings Subjected to Typical Subduction Earthquake Motions for the Mexican Pacific Coast

1997 ◽  
Vol 13 (3) ◽  
pp. 505-532 ◽  
Author(s):  
Arturo Tena-Colunga ◽  
Consuleo Gómez-Soberón ◽  
Abel Mun~oz-Loustaunau
Keyword(s):  
Dynamic Stability ◽  
Pacific Coast ◽  
Base Isolation ◽  
Time History ◽  
Mode Shapes ◽  
Soil Conditions ◽  
Original Design ◽  
Mexican Pacific ◽  
Fixed Base ◽  
Isolation Systems

An analytical study on the application of different base isolation systems for original design or retrofit of typical building structures of the Mexican Pacific Coast is presented. The subject hypothetical buildings are located on hard soil conditions at Acapulco. Typical accelerograms for the Mexican subduction zone recorded during recent earthquakes were used for 3-D time-history analyses. Bidirectional input was used for the time-history analyses. The studied base isolation systems reported in this study are lead-rubber bearings (LRB) and steel-hysteretic dampers (SHD). For the original design case studies, the superstructures were designed: a) according to the seismic provisions of the building code of Guerrero state (RCGS-90) for the fixed-base condition and, b) according to an elastic design based upon a 3-D lateral force distribution consistent with dominant mode shapes for the isolated structure to yield the peak dynamic base shear transmitted by the isolation system. Material volumes for the superstructure were estimated for both the fixed-base code designs and the base-isolation designs. Important savings on the volume of concrete and steel reinforcement can be attained for the base isolated designs with respect to their counterpart fixed-base designs. Dynamic responses for the isolated structures compare favorably with those for the fixed-base structures. The study confirms many findings published in the literature regarding the effectiveness of base isolation and the effect of torsional responses. However, the study also shows that the dynamic stability of isolators is not always achieved using rational design procedures. The dynamic stability and design of the studied base isolators can be controlled by acceleration records associated to moderate earthquakes when these records are near the fault plane and by torsional responses.

scholarly journals Evaluating Collapse Fragility Curves for Existing Buildings Retrofitted Using Seismic Isolation

2020 ◽  
Vol 10 (8) ◽  
pp. 2844
Author(s):  
Amedeo Flora ◽  
Giuseppe Perrone ◽  
Donatello Cardone
Keyword(s):  
Seismic Isolation ◽  
Failure Modes ◽  
Base Isolation ◽  
Fragility Curves ◽  
Limit State ◽  
Spectral Acceleration ◽  
Existing Buildings ◽  
Isolation System ◽  
Isolation Technique ◽  
Design Earthquake

Few studies have investigated so far the collapse capacity of buildings with base-isolation. In such studies, preliminary considerations have been drawn based on a number of assumptions regarding: (i) the methodology used for assessing the collapse capacity, (ii) the collapse conditions and failure modes assumed for both superstructure and isolation system, and (iii) the numerical modeling assumptions. The main results pointed out that the collapse conditions of base-isolated buildings may occur for intensity levels slightly higher than those associated with the design earthquake. In this paper, further developments are made through the use of enhanced models for the description of the behavior of a rubber-based isolation system and the assumption of more rational collapse conditions. Collapse fragility functions, in terms of mean and dispersion values, are proposed for two archetypes representative of existing buildings retrofitted using the seismic isolation technique. The collapse margin ratio (median collapse capacity Sa,C, namely the spectral acceleration associated to a probability of exceedance equal to 50%, divided by the design spectral acceleration at the collapse prevention limit state) has been evaluated for each examined case-study. Values ranging from 1.10 to 1.45 were found.

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