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Seismic Isolation for Small Seismic Isolation for Small Reinforced Concrete StructuresReinforced Concrete Structures
A Preliminary Investigation on Material CostA Preliminary Investigation on Material CostA Preliminary Investigation on Material Cost
Investigated and Presented by:Investigated and Presented by:
Abiel Carrillo
Advisor:
Dr. George C. LeeSamuel P. Capen Professor
Advisor:
Dr. George C. LeeSamuel P. Capen Professor
Abiel Carrillo
Multidisciplinary Center for Earthquake Engineering Research
ObjectiveObjective
The objective of this The objective of this investigation is to show investigation is to show the effectiveness of a the effectiveness of a specific rubber bearing specific rubber bearing isolation design of a isolation design of a symmetrical, lowsymmetrical, low--rise rise reinforced concrete reinforced concrete structurestructure in the region of in the region of Algeria, AfricaAlgeria, Africa
Multidisciplinary Center for Earthquake Engineering Research
Motivation for this investigationMotivation for this investigation
One evening in May, 2003, Algeria was struck by its worst earthquake in 23 years. More than 2,000 people were killed and over 9,000 injured. Many homes were destroyed in the initial quake and thousands more were damaged and made uninhabitable.
One evening in May, 2003, Algeria was struck by its worst earthqOne evening in May, 2003, Algeria was struck by its worst earthquake uake in 23 years. More than 2,000 people were killed and over 9,000 in 23 years. More than 2,000 people were killed and over 9,000 injured. Many homes were destroyed in the initial quake and injured. Many homes were destroyed in the initial quake and thousands more were damaged and made uninhabitable.thousands more were damaged and made uninhabitable.
Multidisciplinary Center for Earthquake Engineering Research
A1
Motivation for this investigationMotivation for this investigation
To explore a system To explore a system that could protect that could protect similar structures, similar structures, preventing disasters preventing disasters like this.like this.
Multidisciplinary Center for Earthquake Engineering Research
Slide 5
A1 Some structures experienced non structural damage, others buckled, other completely destroyedAbiel Carrillo, 7/25/2004
ObjectiveObjective
As will be explained later, base isolation in general can be one of the safest or most cost effective ways of designing a structure in a highly seismic zone. The results of this investigation, focus on a specific example.
As will be explained later, As will be explained later, base isolation in general base isolation in general can be one of the safest can be one of the safest or most cost effective or most cost effective ways of designing a ways of designing a structure in a highly structure in a highly seismic zone. The results seismic zone. The results of this investigation, focus of this investigation, focus on a on a specific examplespecific example..
Multidisciplinary Center for Earthquake Engineering Research
OverviewOverview
oo Method and Codes Method and Codes oo Design Loads Design Loads oo Parameters and AssumptionsParameters and Assumptionsoo Base IsolationBase Isolationoo Summary of ResultsSummary of Resultsoo ConclusionsConclusionsoo ReferencesReferences
Multidisciplinary Center for Earthquake Engineering Research
Method and Codes Used
Two possible frames were designed, A and B, and the total required material was then compared:
A. Moment resisting frame B. Base isolated frame
Isolator
Multidisciplinary Center for Earthquake Engineering Research
Method and CodesMethod and Codes
The design steps for base isolation ultimately shift the frame’s period.
Acceleration is significantly reduced, which means that smaller lateral forces are developed
Multidisciplinary Center for Earthquake Engineering Research
Method and Codes
! American Concrete Institute (1999)For floor system, girder, column and foundation design.
! Uniform Building Code (1997)For design loads and base isolation design.
! Algerian Seismic CodeFor Equivalent static earthquake loading applied to moment frame A
Multidisciplinary Center for Earthquake Engineering Research
Design LoadsDesign Loads
!Earthquake loads were determined from a static lateral equivalent calculation based on Algerian Seismic Codes.
!!Earthquake loads were determined from a Earthquake loads were determined from a static lateral equivalent calculation based static lateral equivalent calculation based on Algerian Seismic Codes. on Algerian Seismic Codes.
72 kip72 kip
40 kip40 kip
Multidisciplinary Center for Earthquake Engineering Research
Parameters and Assumptions
Steel Steel ffyy 60 60 ksiksi
Conc. Conc. ff’’cc 3 3 ksiksi
Allowable
Details were as follows:Details were as follows:
90 ft
Allowable Soil stressSoil stress 4 4 ksiksi
90 ft
27 ft
OccupancyOccupancy OfficesOffices
Seismic Seismic ZoneZone 33
Dead LoadDead Load 12 12 psfpsf
Roof LiveRoof Live 20 20 psfpsf
Floor LiveFloor Live 50 50 psfpsf
Multidisciplinary Center for Earthquake Engineering Research
Base Isolation DesignBase Isolation Design
There are various isolation methods and devices available and are being developed, and the Code does not “prefer” a type, nevertheless it requires that the system have the following three properties:
1. Be stable for the required displacement
2. Provide increasing resistance with increasing displacement
3. Does not degrade under cyclic loading
Multidisciplinary Center for Earthquake Engineering Research
A2
Base Isolation DesignBase Isolation Design
Selected Isolation: High Damping Rubber Bearing
Thin steel shims (circular plates) increase bearing strength
Thin steel shims (circular plates) increase bearing strength
Rubber cylinder
Steel plate
Multidisciplinary Center for Earthquake Engineering Research
Slide 14
A2 There are many others which i encourage you to look at but in the interest of time..Abiel Carrillo, 7/25/2004
A3
Base Isolation DesignBase Isolation Design
Steps for a Code based design:Steps for a Code based design:
1. Determine and establish parameter-dependent factors.
2. Select a type of bearing and estimate target values, such as stiffness, damping ratio and bearing displacement.
3. Relate required dimensions of the isolation bearing unit with target values from step 2.
4. Detail actual dimensions for isolation unit.
1. Determine and establish parameter-dependent factors.
2. Select a type of bearing and estimate target values, such as stiffness, damping ratio and bearing displacement.
3. Relate required dimensions of the isolation bearing unit with target values from step 2.
4. Detail actual dimensions for isolation unit.
Multidisciplinary Center for Earthquake Engineering Research
Slide 15
A3 There are many steps but basically...Abiel Carrillo, 7/25/2004
Summary of ResultsSummary of Results
The resultant design called for 16 units with the following dimensions:
17 ” rubber diameter
11 “ height
12 gage shims
Multidisciplinary Center for Earthquake Engineering Research
Summary of ResultsSummary of Results
AAA
A / B weight ratios of main structural elementsA / B weight ratios of main structural elements
Concrete ratio Steel ratio
Girders 1.71.7
1.51.5
2.32.3
4.94.9 Steel in Base Isolated frame is Steel in Base Isolated frame is not continuousnot continuous
Columns 3.23.2 A minimum amount of concrete A minimum amount of concrete required in both columnsrequired in both columns
Foundations 1.81.8 Same rebar diameter, just larger Same rebar diameter, just larger dimensionsdimensions
B
Multidisciplinary Center for Earthquake Engineering Research
ConclusionsConclusions
! Base Isolators can be expensive, but the rubber bearings chosen are very common. The final design calls for 16 units, which doesn’t compare to having a total of 3.3 times more steel as required in the larger reinforced frame.
Multidisciplinary Center for Earthquake Engineering Research
ConclusionsConclusions
! Results for other structures can vary significantly
Factors that influence structural design:
- Importance of building- Soil profile- Availability and shipping- Height of structure- Labor - Site plan- Architectural requirements- Other factors
! Results for other structures can vary significantly
Factors that influence structural design:
- Importance of building- Soil profile- Availability and shipping- Height of structure- Labor - Site plan- Architectural requirements- Other factors
Multidisciplinary Center for Earthquake Engineering Research
ConclusionsConclusions
! Base Isolation also protects non-structural elements and equipment by reducing the entire structure’s acceleration during an earthquake, as opposed to reinforcement alone.
! Base Isolation also protects non-structural elements and equipment by reducing the entire structure’s acceleration during an earthquake, as opposed to reinforcement alone.
Frame is still standing but non-bearing walls could not withstand the strong shaking.
Frame is still standing but non-bearing walls could not withstand the strong shaking.
Multidisciplinary Center for Earthquake Engineering Research
A5
Slide 20
A5 include equipment isolation, like in a museumAbiel Carrillo, 7/26/2004
ReferencesReferences
! Paz, Mario. International Handbook of Earthquake Engineering : Codes, Programs and Examples.October, 1994; Chapman and Hall. London, England.
! McCormack, Jack. Design of Reinforced Concrete.2001; John Wiley & sons, Inc. New York, New York.
! Kelly, James M.; Naeim, Farzad. Design of Seismic Isolated Structures: From Theory to Practice.1999; John Wiley & sons, Inc. New York, New York.
Multidisciplinary Center for Earthquake Engineering Research
AcknowledgementsAcknowledgements
! - Multidisciplinary Center for Earthquake Engineering Research
! Dr. George C. Lee
Samuel P. Capen Professor
! Civil Engineering Dept. , Univ. at Buffalo
Multidisciplinary Center for Earthquake Engineering Research
“One's mind, once stretched by a new idea, never regains its original dimension.”
- Oliver Wendell Holmes