The document discusses the dynamic response of a 14-storey reinforced concrete frame building using base isolators. It aims to analyze the response of the building with and without base isolators, including lead rubber bearings and sliding bearings, under earthquake ground motions. The analysis is performed using the finite element software ETABS. The results show that base isolation is effective at reducing seismic responses like displacement, acceleration, base shear and storey drift compared to a fixed base building. PTFE isolators provide more reduction than LRB isolators in most responses. Irregularities in building plan and elevation also increase the response of a fixed base building.
Base isolation is one of the most widely accepted seismic protection systems in earthquake prone areas. It mitigates the effect of an earthquake by essentially isolating the structure from potentially dangerous ground motions, especially in frequency range where building is mostly affected. This includes
Concept of Base Isolation
Principle of Base Isolation
Comparison of Fixed Base Structure and Isolated Base Structure
Types of Isolation Components
Base Isolation in Real Buildings
Applications of Base Isolation
Report on Study on Base Isolation Techniques.Gaurav Mewara
Base Isolation technique is on of the advance technique used for construction of earthquake resisting sturcture.
All earthquake resisting structure are based on this technique.
This consit report on study of base isolation with its advantages disadvanges.
Base isolation is one of the most widely accepted seismic protection systems in earthquake prone areas. It mitigates the effect of an earthquake by essentially isolating the structure from potentially dangerous ground motions, especially in frequency range where building is mostly affected. This includes
Concept of Base Isolation
Principle of Base Isolation
Comparison of Fixed Base Structure and Isolated Base Structure
Types of Isolation Components
Base Isolation in Real Buildings
Applications of Base Isolation
Report on Study on Base Isolation Techniques.Gaurav Mewara
Base Isolation technique is on of the advance technique used for construction of earthquake resisting sturcture.
All earthquake resisting structure are based on this technique.
This consit report on study of base isolation with its advantages disadvanges.
Seismic performance of adjacent building using fluid viscous dampersAyaz Malik
This presentation highlights the effect of Fluid Viscous Dampers (FVDs) on the seismic performance of adjacent buildings connected through a ped-way. A part of this project also deals with the Qualitative Damage Analysis of the structure during an earthquake, with and without FVDs.
Seismic retrofitting is a collection mitigation technique for earthquake engineering.
It is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquake.
It is of utmost important for historic monuments, areas prone to severe earthquakes and tall or
expensive structures.
The retrofitting techniques are also applicable for other natural hazards such as tropical cyclones, tornadoes and severe winds from thunderstorms.
Retrofitting proves to be a better economic consideration and immediate shelter to problems
rather than replacement of building.
Base isolation system consists of isolation units with or without isolation components, where: Isolation units are the basic elements of a base isolation system which are intended to provide the aforementioned decoupling effect to a building or non-building structure. Isolation components are the ...
base isolation systems
base isolation system in building
base isolation pdf
base isolation definition
base isolation foundation
base isolation cost
base isolation techniques
base isolation pads
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The process in which the response of the soil influences the motion of the structure and the motion of the structure influences the response of the soil is termed as soil-structure interaction (SSI)
Seismic performance of adjacent building using fluid viscous dampersAyaz Malik
This presentation highlights the effect of Fluid Viscous Dampers (FVDs) on the seismic performance of adjacent buildings connected through a ped-way. A part of this project also deals with the Qualitative Damage Analysis of the structure during an earthquake, with and without FVDs.
Seismic retrofitting is a collection mitigation technique for earthquake engineering.
It is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquake.
It is of utmost important for historic monuments, areas prone to severe earthquakes and tall or
expensive structures.
The retrofitting techniques are also applicable for other natural hazards such as tropical cyclones, tornadoes and severe winds from thunderstorms.
Retrofitting proves to be a better economic consideration and immediate shelter to problems
rather than replacement of building.
Base isolation system consists of isolation units with or without isolation components, where: Isolation units are the basic elements of a base isolation system which are intended to provide the aforementioned decoupling effect to a building or non-building structure. Isolation components are the ...
base isolation systems
base isolation system in building
base isolation pdf
base isolation definition
base isolation foundation
base isolation cost
base isolation techniques
base isolation pads
interesting civil engineering topics
civil engineering topics for presentation
civil seminar topics ppt
civil engineering seminar topics 2018
seminar topics pdf
best seminar topics for civil engineering
seminar topics for mechanical engineers
latest civil engineering seminar topics
The process in which the response of the soil influences the motion of the structure and the motion of the structure influences the response of the soil is termed as soil-structure interaction (SSI)
Study on laminated rubber bearing base isolators for seismic protection of st...eSAT Journals
Abstract
Base isolation or seismic base isolation is an effective means for protection of structures, its contents and its occupants during the event of an earthquake. The principle of base isolation is vibration isolation. It decouples the building from damaging action of the earthquake. The isolator partially reflects and partially absorbs input seismic energy before it gets transmitted to the superstructure. Laminated Rubber Bearing Isolators are placed between the superstructure and foundation, which reduces the horizontal stiffness of the system. It thereby increases the time period of the structure and decreases the spectral acceleration of the structure. The superstructure acts like a rigid body, thus inter storey drift is reduced. Such type of isolators are used in practice in India, yet a proper design procedure based on IS code is unavailable. The paper presents design procedure for LRB adopting the procedure of IS 1893:2002 (Part-1) for earthquake resistant design of buildings. Design charts have been developed and presented in this paper which gives isolator diameter and rubber thickness as design outputs. The design procedure requires different input parameters like fundamental period and damping of the fixed base structure, axial load on the column, seismic zone, type of soil and shore hardness of rubber. These design charts enable the designer to easily arrive at the isolator parameters to achieve seismic isolation. Using the charts, case study has been done using SAP2000. Building displacement and acceleration are compared for model with and without base isolator. Comparative study of linear and non-linear base isolators has also been carried out. Linear and non-linear time history analysis has been done using El Centro earthquake.
Keywords: base isolation, laminated rubber bearing, IS Code, seismic protection, design charts, time history analysis, SAP2000
Seismic analysis of high damping rubber bearings for base isolationeSAT Journals
Abstract
Base isolation is a mechanism that provides earthquake resistance to the new structure. The base isolation system decouples the building from the horizontal ground motion induced by earthquake, and offers very stiff vertical components to the base level of the superstructure in connection to substructure (foundation). It shifts the fundamental lateral period, dissipates the energy in damping, and reduces the amount of the lateral forces that transferred to the building, inter-story drift, and the floor acceleration.
The work deals with modelling and finite element analysis of a high damping rubber bearing in ANSYS 12.0. A displacement controlled transient analysis was done to analyse the behaviour of the isolator during earthquakes.
Keywords: Base isolation, High damping rubber, Transient analysis
Eatrhquake response of reinforced cocrete multi storey building with base iso...eSAT Journals
Abstract A seismic base isolation is an earthquake resistant design method that is based on reducing the seismic demand and also the ductility demand. The basic concept of base isolation system is to increase the natural time period of the fixed base building and to protect the structure from the seismic effect. The main purpose of this work is to study the dynamic response of structure when subjected to different isolators. For this purpose, a three dimensional response spectrum analysis and time history analysis is performed using a commercial structural analysis software package called as SAP 2000 to study the influence of isolation damping on building. The main objective is to make a comparison between the fixed base building and various isolation systems such as friction pendulum isolator, lead rubber bearing (LRB) isolator and high damping rubber isolator, subjected to strong earthquakes to achieve an optimal design of the base isolation system. SAP 2000, a popular large scale explicit finite element analysis software used to stimulate the behavior of base isolated structure. In the present work, it was found that base isolation substantially increases the time period of structure and hence correspondingly reduces the base shear. The top displacement for fixed and isolated cases conspicuously shows the reduction in the case of isolated frame. The study shows that the bending moment and shear force values are reduced for base isolated frame when compared to fixed base building. From design consideration the steel requirement is reduced in base isolated structures when compared to fixed base building. Key Words: Isolators, SAP2000
Comparison of Two Similar Buildings with and without Base IsolationIJARIIT
Reinforced concrete is a major construction material for civil infrastructure in current society.
Construction design has always preceded the development of structural design methodology. Dramatic collapse of
buildings has been observed after each disastrous earthquake, resulting in loss of life. To prevent such a loss Baseisolation
is used which enables a building to survive potentially devastating seismic impact by providing flexibility into
the connection between the building and the foundation. The mechanism of the base isolator increases the natural
period of the overall structure, and decreases its acceleration response to earthquake/seismic motion. A reinforced
concrete building with lead rubber bearing is used. The study analysis performed to check for the adequacy of the
base isolation against earthquake damage when compared to the conventional earthquake resistant design. A building
was analyzed using the equivalent lateral force method and response spectrum analysis as fixed base (FB) and as
isolated base (IB) with lead rubber bearing. The analysis represents a case study for reinforced concrete to show the
ultimate capacity of the selected bearing system, and to make a comparison for the difference between the isolated
base and the fixed base buildings. R esults show that the presence of the lead rubber bearing reduces significantly the
displacement, moment and shear generated for the same mode and hence the reinforcement required is also lesser
when compared to the traditional fixed based structure.
In this presentation i have gone through about various prospects and challenges that have been faced at the time of installation,its types,method of installation &its application.
ELASTOMERIC BASE ISOLATION SYSTEM FOR SEISMIC MITIGATION OF LOW-RISE STRUCTURESIAEME Publication
Seismic base isolation is a passive way of achieving seismic response control by introducing isolators between foundation and super structure. Isolator performs three functions: horizontal flexibility, energy dissipation and rigidity against normal lateral loads. Lead Rubber bearing isolators
performs these functions efficiently. By reducing the horizontal stiffness of the system, it increases the time period of the structure and decreases the spectral acceleration of the structure. The superstructure acts like a rigid body, thus inter storey drift is reduced. Such type of isolators are used
in practice in India, yet a proper design procedure based on IS code is unavailable. The paper presents design procedure for LRB adopting the procedure of IS 1893:2002 (Part-1) for earthquake resistant design of buildings.
A mass damper is a vibration absorber able to attenuate the vibrations of a structure or a machinery. By a mass damper it's possible to increase the global damping of the system without the necessity to modify the mechanical structure.
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1. DYNAMIC RESPONSE OF RC FRAME
BUILDING USING BASE ISOLATORS
GUIDED BY,
B S JAYASHANKAR BABU
ASSOCIATE PROFESSOR,
DEPARTMENT OF CIVIL
ENGINEERING.
PREMKUMAR M K
4th sem, M.Tech,
CAD structures,
PESCE.
2. INTRODUCTION
Earthquakes cause inertia forces proportional to the product of the building
mass and the ground accelerations.
Due to this mass asymmetry in building center of mass is shifted from
center of stiffness causing eccentricity. As this eccentricity increases, torsion
in building also increases.
As the ground accelerations increases, the strength of the building must be
increased to avoid structural damage.
It is not practical to continue to increase the strength of the building
indefinitely.
Base isolation is one of the most widely accepted techniques to protect
structures and to mitigate the risk to life and property from strong
earthquakes.
3. OBJECTIVES
To find out the response of 14 storey RC bare frame with and without base
isolator (i.e., Mode period, displacement, acceleration, base shear, storey
drift) by response spectrum analysis. Numerical modelling and analysis are
carried out using finite element based software ETABS.
To study the response of base isolated building using lead rubber bearing
and sliding bearing system for bare frame of symmetric model using time
history analysis of El Centro earthquake data.
To compare the performance of RC bare frame having plan and elevation
irregularities with and without base isolator.
Study of isolation system variations and isolation system hysteresis in case
of lead rubber bearing (LRB) and PTFE system.
4. LITERATURE REVIEW
Bill Robinson et al. (1993), have written a book called seismic isolation for
designers and structural engineers. This book gives total insight into the
practical methods of construction of seismically isolated buildings. The
different types of isolation devices and their properties are discussed here.
W h Robinson (1997), describes the principles of seismic isolation and discuss
some of the isolation systems available before giving some examples of the
application of seismic isolation to structure in new Zealand.
M Kikuchi and S Kamamato (2007), presents an analytical model for lead-
rubber bearing to predict bearing force-displacement behavior under extremely
large deformations.
5. LITERATURE REVIEW
Kaab mohamed zohair (2011), presented the use of the base isolation device
LRB (lead rubber bearing) allows the control of the deformation which are
localized on this last, and also allows carrying out a satisfactory compromise
between the reduction of the seismic forces and the increase in the
deformations of the base isolation.
Kelly et al., studied the effectiveness of seismic base isolation in controlling
the deformations in prefabricated concrete structures. When utilized in
prefabricated concrete structures seismic base isolation has the potential to
reduce the ductility demand from these structures under seismic loading.
6. BASE ISOLATION:
Base isolation is a passive vibration control system.
The goal of base isolation is to reduce the energy that is transferred
from the ground motion to the structure.
(a) Conventional structure (b) base isolated structure.
7. THE PURPOSE OF BASE ISOLATION
As for all the load cases encountered in the design process, such as
gravity and wind, should work to meet a single basic equation:
CAPACITY > DEMAND.
This can be achieved by,
Ductility
Leads to higher floor accelerations.
Damage to structural components, which may not be repairable.
EFFECTS OF DUCTILITY
8. TYPES OF ISOLATOR
Lead rubber bearing (LRB)
Flat sliding bearing (PTFE)
COMPONENTS OF LRB
10. DESIGN OF ISOLATOR
1. A displacement is assumed, using the total rubber thickness as a starting
point.
2. The effective stiffness of the bearing at this displacement is calculated.
3. The effective period is calculated using the total seismic mass and the
effective period.
4. The equivalent viscous damping is calculated from the area of the
hysteresis loop. For HDR, the damping and shear modulus are
interpolated from tabulated values of these quantities versus shear strain.
5. The damping factor, b, is calculated for the equivalent viscous damping.
6. The spectral displacement is calculated from the acceleration response
spectrum at the effective period, modified by the damping factor b.
7. This displacement is compared with the displacement assumed in step 1.
Above. If the difference exceeds a preset tolerance, the calculated
displacement defines a new starting displacement and the procedure is
repeated until convergence is achieved.
12. DETAILS OF RC FRAME
Number of bays in x-direction = 6 bay
Number of bays in y-direction = 3 bay
Number of storeys = 14 storey (G +13)
Bottom storey = 3.0 m
Other storeys = 3.0 m
Link element = 0.5 m
Beam size = 0.7 m x 0.4 m
Column size = 0.5 m x 0.5 m
Slab thickness = 0.15 m
Live load on the slab = 3 kN /m2
13. NONLINEAR LINK TYPE: LRB ISOLATOR
U1 Linear effective stiffness = 1253000 kN/m
U2 and U3 Linear effective stiffness = 1174 kN/m
U2 and U3 Nonlinear stiffness = 8599 kN/m
U2 and U3 Yield strength = 117 kN
U2 and U3 Post yield stiffness ratio = 0.09
14. NONLINEAR LINK TYPE: PTFE ISOLATOR
U1 Linear effective stiffness = 5000000 kN/m
U1 Nonlinear effective stiffness = 5000000 kN/m
U2 and U3 Linear effective stiffness = 2038 kN/m
U2 and U3 Nonlinear stiffness = 2000000 kN/m
U2 and U3 Friction coefficient, slow = 0.04
U2 and U3 Friction coefficient, fast = 0.06
U2 and U3 Rate parameter = 40
U2 and U3 Radius of sliding surface = 0
15. FIXED BASE MODE PERIOD AND LRB BASE ISOLATED
MODE PERIOD
Mode
number
Fixed base mode period
(Ts)
Base isolated mode period
(Tb)
1 1.4801 3.0809
2 1.4316 3.0526
3 1.4284 2.9881
16. RESPONSE OF SYMMETRIC MODEL OF FIXED BASE AND
LRB BASE ISOLATED BUILDING
Floor level vs. lateral displacements graph Floor level vs. storey drift graph
17. RESPONSE OF SYMMETRIC MODEL OF FIXED BASE AND
LRB BASE ISOLATED BUILDING
Floor level vs. acceleration graph Floor level vs. storey shear graph
18. MODE PERIODS OF THE FIXED BASE AND PTFE BASE
ISOLATED BUILDING
Mode number Fixed base mode period
(Ts)
Base isolated mode period
(Tb)
1 1.4801 2.5505
2 1.4316 2.5329
3 1.4284 2.4816
19. RESPONSE OF SYMMETRIC MODEL OF FIXED BASE AND
PTFE BASE ISOLATED BUILDING
Floor level vs. Lateral displacements graph floor level vs. Storey drift graph
20. RESPONSE OF SYMMETRIC MODEL OF FIXED BASE AND
PTFE BASE ISOLATED BUILDING
Floor level vs. Acceleration graph Floor level vs. Storey shear graph
22. MODE PERIODS OF THE FIXED BASE BUILDING FOR
ASYMMETRIC MODELS (P1 AND P2)
Mode
number
Fixed base FBP1
(Ts)
Fixed base FBP2
(Ts)
1 1.4830 1.4729
2 1.4230 1.3597
3 1.3894 1.2579
23. RESPONSE OF PLAN ASYMMETRIC MODEL OF FIXED
BASE BUILDING
Floor level vs. Lateral displacement graph Floor level vs. Storey drift graph
24. RESPONSE OF PLAN ASYMMETRIC MODEL OF FIXED
BASE BUILDING
Floor level vs. Acceleration graph Floor level vs. Storey shear graph
28. The north-south component of the ground motion at El Centro, California
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 5 10 15 20 25 30 35
ACCELERATION(m/s2)
TIME (sec)
El CENTRO GRAPH
37. FUTURE SCOPE OF STUDY
The study on optimal base isolation system of multistory RC frame
buildings in a probabilistic sense.
Study on laminated rubber bearing constructed with scrap tires filled
crushed rock as bearing to reduce manufacturing costs.
With recent advancement in material technology, more study can be
focused on material qualities used in isolators like their strength,
durability, high vertical stiffness, low horizontal stiffness and high energy
dissipating capacity.
38. CONCLUSIONS
Natural period of the structure increases in case of base isolated building in
comparison with fixed base building
Base isolation reduces the seismic response of plan and vertical irregular
models
Base shear, acceleration, storey drift decreases whereas generally lateral
displacement increases in base isolated building.
Fixed base buildings have zero storey acceleration at base of building
whereas, in case of base isolated building appreciable amount of storey
acceleration will been found out at base.
In case of PTFE base isolated building, reduction in response is more for
=0.06 rather than =0.15.
39. In case of PTFE base isolated building, reduction in response is more for =0.06
rather than =0.15.
PTFE isolator alone cannot be used in a building because it has no restoring
force in the system and results in large lateral displacement
Lead rubber bearing effectively reduces 70% of the base shear in the building.
In case of LRB isolation system variations, with increase in time period
displacement and damping of the system increases.
In case of PTFE isolation system variations, with increase in time period
displacement increases. Damping remains constant for all values of time period.
40. REFERENCES
Ivan skinner, R., Trevor E. Kelly and bill robinson, W. H. (1993), A text
book on seismic isolation for designers and structural engineers, robinson
seismic limited, holmes consulting group.
W. H. Robinson (1998), “passive control of structures, new zealand
experience”, ISET, journal of earthquake technology.
Kelly et al. Uasge of seismic base isolation to reduce the ductility demand
from prefabricated concrete structure, holmes consulting group limited.
Trevor e kelly, s. E. (2001), design guidelines on base isolation of
structures, holmes consulting group, new zealand.
Pankaj agarwal and manish shirkhande. (2010), A text book on earthquake
resistant design of structures, PHI learning private limited, new delhi.
Anil k. Chopra, dynamic of structures, theory and application to
earthquake engineering, third edition.
Wai-fah chen charles scawthorn, “earthquake engineering handbook”.