Shake Table Prashant 14

8/14/2019 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

materials 13


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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

06/07/08 19:11 1717


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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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Max Acceleration=0.71 g at 7.5

sec


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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

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Shake Table Prashant 14