Download - Shake Table Prashant 14
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X - axis
Y - axis
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Group Members Analysis Group
Prashant Savaliya (PM) Jesus E. Carrillo (APM) Phu Nguyen Nham Nguyen Steven Wang
Experimental Group Francisco J. Jaime Jr. (APM) Rafael A. Donado Farzaneh Mousavi Ike Ogiamien
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Overview Concepts of Earthquakes Structural Protection Systems
3D Steel Moment Frame Structure Experimental Computer Analysis
2D Steel Structure Experimental
Computer Analysis Timber Structure
Experimental
Conclusion
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Concepts of Earthquakes Caused by a sudden slip on a fault.
Occurs when plates grind and scrape against eachother.
The Pacific Plate and the North American Plate. Earthquakes occur on faults.
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Types of Geological Faults
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Normal Fault
Thrust Fault
Strike SlipFault
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Tectonic Plates
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Seven (7) major and
minor plates
Earthquakes,
volcanic activity, occur
along plate boundaries
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Major Faults of California Local Major Faults
San Andreas fault(Lateral fault)
Loma Prieta Earthquakeproduced by SanAndreas fault
Santa Monica Fault San Gabriel Fault
Blind Faults Northridge Earthquake
http://education.usgs.gov/california/maps/faults_names2.htm
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Northridge EarthquakeRevealed buildings that were not built to code
Failure of Moment-Frame structures
Insufficient design of connections
Failure of non-structural elements
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Northridge Earthquake
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Northridge Earthquake January 17, 1994
Magnitude of 6.5
57 killed
12,000 injured.
$12.5 billionDamages
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Structural Protective
Systems Viscous Damper Friction Damper Mass Damper Base Isolator
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Viscous Dampers Functions like an
automobiles shockabsorber
Reduces displacement
High acceleration
resistance
Reduction in story drift
Utilizes less construction
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Application of Viscous
Dampers
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Friction Dampers
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Utilize friction powerto absorb vibration
energy
Increases stiffness ofthe structure
Limiting base sheardemands onstructural
foundations
Friction Damper
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Tuned-MassDamper Function like an inverted
pendulum
Dissipates energy createdby the motion of its mass
Creates an equal andopposite force to resistmotion
Resist lateral forces anddisplacement ofstructures
Reduces resonanceresponse
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Ta
ipe
I1
01
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Base Isolator
Allows the building
foundation to movewith the ground
Flexes laterally to
reduce the groundmotion fromaffecting thestructure
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Analyzing the Structures
3D Steel Moment Frame Structure 2D Steel StructureTimber Structure
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Free Vibration
Free Vibration without Mass Damper
-3
-2
-1
0
1
2
0 2 4 6 8 10 12
Time (sec)
Acceleration(g)
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10 Cycles in 4.5 Sec.
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Prototype Steel Moment-Frame
Structure
From Free Vibration
Time measuredduring 10 cycles:4.5 seconds
ExperimentalFundamentalperiod: 0.45 sec
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SAP Modeling
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M d l P i d ith Pi d
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Modal Period with PinnedBase
T1 = 0.48 sec, f1 = 2.1
Hz
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Modal Period with Fixed Base
T1 = 0.42 sec, f1 = 2.4
Hz
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Experimental Determination
of Fundamental Period
In conclusion, the support of thestructure at the base behavessomewhere between pinned and
fixed.
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Resonance Effect
Cyclic Frequency (Hz) Acceleration (g)
1.00 0.13
1.50 0.30
2.00 0.90
2.25 1.80
2.50 3.50
2.75 2.00
3.00 1.40
3.50 0.70
4.00 0.40
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Resonance Effect(Acceleration vs. Frequency)
Natural Frequency f1=2.4 Hz (from SAPanalysis)
The maximum acceleration response occurs for
f=2.5 Hz Acceleration vs. Frequency
0
0.5
1
1.5
2
2.5
3
3.5
4
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Frequency (Hz)
Accelera
tion
(g)
Acceleration vs. Frequency
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Mexico City Earthquake
Resonance Natural period of the
ground vibration wasabout 2 seconds.
Buildings between10-25 stories havenatural periods ofabout 2 seconds.
Natural frequency ofthe building wassimilar to resonancefrequency of seismicloading from soil
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Time-history Analysis underNorthridge Earthquake
Ground motion at the HollywoodStorage station is used for the
seismic analysis.
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Ground Motion Acceleration
Time History(x-direction)
Ground Accelerations vs. Time
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0 5 10 15 20 25 30 35 40
Time (second)
Acceleration
(g)
X direction
Peak ground acceleration is 0.231 g 32
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Ground Motion Acceleration
Time History(y-direction)
Ground Accelerations vs. Time
-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 40
Time (second)
Acceleration
(g)
Y direction
Peak ground acceleration is 0.358 g 33
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Measured Acceleration Response onConventional System at 4th Level
Maximum acceleration response is 1.03 g34
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Measure Acceleration Response onConventional System at 4th Level
Maximum acceleration response is 1.705 g 35
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Acceleration Response atVarious Levels of Structure
0
0.4
0.8
1.2
1.6
2
0 1 2 3 4 5 6 7
Floor Level
Acceleration(g
Story Force=Acceleration x Floor Mass36
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Tuned-Mass Damper IllustrationUsing Shake Table Analysis
Weights are addedto the top of theexperimental steelstructure toillustrate theconcept of tuned-mass damping
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Big Steel Frame with MassDamper Attached during
ExperimentMass Damper
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Measured Acceleration Responsewith Mass Damper
Maximum acceleration response is 0.756 g at 8.7 second. 40
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4th Level Measured Acceleration Responseof Conventional System and DampedSystem
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4th Level Measured Acceleration Responseof Conventional System and DampedSystem
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Lateral Displacement
1
2
3
4
5
6
7
0 0.5 1 1.5
Lateral Displacement (in.)
FloorLevel
Conventional Damped 44
Comparison between
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Comparison betweenConventional System andDamped System
Max. Acceleration Column Moment
Conventional 1.03 g 191 in-lb
With Mass Damper 0.58 g 121 in-lb
Reduction (%) 43.7 % 36.7 %
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2D Steel Frame PrototypeStructures
Seismic Excitationonly in one direction
Height: 54.5 in Width: 6.25 in 10N weight
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Free Vibration Graph
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Free Vibration Graph
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SAP Model
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Modal Period for 2D Steel Frame
T1 = 0.17 sec, f1 = 5.8
Hz
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Experimental Determination ofFundamental Period
Time measured during 7 cycles:
1.4 seconds Experimental Fundamental Period:
0.20 sec Sap2000 Fundamental Period:
0.17 sec
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Measured Damping Ratio
Using equation:
Damping ratio without fluid dampers : 1.9% Damping ratio with fluid dampers: 4.2% Calculation is based on structural dynamic
theory. 52
%9.1019.0
)5(2
)562.0
023.1
ln(
2
)ln(
==
=
== +
g
g
m
a
a
RatioDamping mn
n
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Demonstration
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Experimental Video on
Timber StructureWithout FrictionDamper With Friction Damper
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Timber Structure-Undamped
Max Acceleration=0.46 g at 7.5
sec.
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Timber Structure-Undamped
Max Acceleration=0.71 g at 7.5
sec
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Timber Structure-Undamped
Max Acceleration=1.0 g at 7.5sec.
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Acceleration Response at VariousLevels
Conventional X-direction Accelerations at Floor
Levels
0.2
0.46
0.71
1
0
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4 5 6 7 8
Floor Level
Flo
orAcceleration(g)
Measured Peak
Acceleration
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IBC-06 Seismic Provisions
V
hw
hwF
k
ii
k
xx
x
=
Vertical Force Distribution
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Conclusion
Our study shows how resonance causesearthquake loads to increasedramatically.
We demonstrated the behavior of threedifferent structures with and withoutdamping systems.
Our experimental data and analyticalresults illustrate that structuralresponse decreases with earthquakeprotection systems.
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The End
Thank You