new trends in dynamic bridge testing the perspective of … · new trends in dynamic bridge testing...

Álvaro Cunha & Elsa CaetanoÁlvaro Cunha & Elsa Caetano

New trends in dynamic bridge testing New trends in dynamic bridge testing The perspective of FEUPThe perspective of FEUP

SUMMARY

• Modal identification• Finite element correlation and updating• Vibration based damage detection• Pedestrian induced vibrations• Traffic induced vibrations• Cable vibrations• Structural monitoring• Control of vibrations

MODAL IDENTIFICATION

Vasco da Gama Bridge

AMBIENT VIBRATION TEST

z

x y

1J

1M2M

2J

3M

3J

5M

5J4M

4J6J

6M7M

7J8J

8M9J

9M10J

10M11J

11M12,13,14M27M

27J12,13,14J

15J

15M16J

16M17J

17M18J

18M19J

19M28J

28M29J

29M

20J

20M

21J

21M22J

22M23J

23M

24J

24M

25J

25M

26M

26J

P1P2

P3PN

PS

P4

P5P6

(North)LISBOA

SETÚBAL(South)

Figure 1: Schematic representation of Vasco da Gama cable-stayed bridge andindication of the measurement sections used in the dynamic tests

6 triaxial accelerographsPrecision: <1g/216=0,015mgSampling frequency: 50 HzFrequency resolution: <0,01Hz

Vasco da Gama Bridge

1st vertical bending mode

2nd vertical bending mode

Free vibration test

Stochastic identification

f=0.338 Hz40,016,0 −=ξ

Free vibration test


f=0.339 Hz41,0=ξ

f=0.456 Hz27,019,0 −=ξ

32,0=ξf=0.457 Hz


1st torsion mode

2nd torsion mode

Free vibration test

f=0.467 Hz36,014,0 −=ξ


f=0.469 Hz34,0=ξ

Free vibration test

f=0.591 Hz39,030,0 −=ξ


f=0.622 Hz


FREE VIBRATION TEST• Identification of modal

damping factors

(b)

p

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Am

plitu

de F

FT (m

g)

GSR-204/206

00.20.40.60.8

11.21.41.61.8

2

100 200 300 400 500 600 700

Envolvente

C urva ajustada 200-500s

ξ=0.24%

-10.00-8.00-6.00-4.00-2.000.002.004.006.008.00

10.00

100 150 200 250 300 350

GSR-200

1/3 span North, half-sum vertical component


Trends for development

• Instrumentation- Wireless solution (time synchronization by GPS)- Conventional cables solution allowing in-situ modal identification

- Innovative data acquisition with local digitizationand signal conditioning, single cable transmissionand remote control from the lab (GSM or Internet)

• Output-only modal identification software- Allowing objective and automatic identification

The old Hintze Ribeiro Bridge

7 spans, 6 masonry piers

Steel truss deck

Wood piles

Construction: 1885 (116 y.o.)

FINITE ELEMENT CORRELATION

COLAPSE OF HINTZE RIBEIRO BRIDGE

March 2001

THE NEW HINTZE RIBEIRO BRIDGE

April 2002


Longitudinalbeam

• Definition of 2 reference stations (6 and 9)• Measurement at supports, midspan, 1/4th span, top and base

of piers

• Measurements along one of the steel I-girders

• 4 seismographs, 18-bit A/Dconverter• 1 laptop


Vertical Direction

4.028

1.465

1.7821.953 2.197

2.539

2.710

2.905

3.5403.809

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

0 1 2 3 4 5

Frequency (Hz)

Am

plitu

de P

SD

N

Average normalized power spectra


-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 50 100 150 200 250 300

Experimental, Freq.=1.451HzNumerical, Freq.= 1.608Hz

Identified vs calculated modes: vertical component

-2

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300

Experimental, Freq.=1.786HzNumerical, Freq.= 1.896Hz


-1

-0.5

0

0.5

1

1.5

2

0 50 100 150 200 250 300

Experimental, Freq.=1.144Hz

Numerical, Freq.= =0.715Hz

Identified vs calculated modes: lateral component

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 50 100 150 200 250 300

Experimental, Freq.=1.641HzNumerical, Freq.= =.892Hz


Calculated frequency (Hz)

Identified frequency (Hz)

Type of mode (*)

1.608 1.465 1st vertical 1.896 1.782 2nd vertical 2.291 2.710 3rd vertical 2.291 2.890 4th vertical 3.458 3.54 5th vertical

Calculated

frequency (Hz) Identified

frequency (Hz) Type of mode (*)

0.715 1.147 1st lateral 0.892 1.636 2nd lateral 1.180 2.881 3rd lateral

Identified vs calculated natural frequencies

Z=120.50

Z=1119.00

Z=126.65

Z=124.50Z=124.50

Z=119.00

7.50 10.00

5.00

10.0061.00

3.0010.00

0.40

28.00

Z=124.50-126.651% 1%

3.800.403.000.40

1.00

0.15

FINITE ELEMENT UPDATING

L1=30m; L2=28m

T0=750kN x 4

Stress-ribbon footbridge

EXPERIMENTAL ASSESSMENT

0.00001

0.0001

0.001

0.01

0.1

0 5 10 15

Frequência (Hz)

PSD

méd

io (m

/s2)

Ref. 1Ref. 2

1 2 3 4 5 6 7 8 Ref 1 Ref 2

9

10 11

12 13 14 15 16 17 18 19 20

Moving measurement points

Reference points


Discretization of the deck in beam finite elements with the geometry corresponding to the design configuration

NUMERICAL MODELLING

Discretization of the deck in beam finite elements with the geometry corresponding to the measured configuration

Model 1

Model 2

-0.500

0.000

0.500

1.000

1.500

2.000

2.500

0 10 20 30 40 50 60

Comprimento (m)

Altu

ra (m

)

Medido

Projecto

Calculado/projecto

Calculado/corrigido

NUMERICAL MODELLING

Discretization of the deck in truss finite elements, with progressive loading and activation of beam elements connecting the nodes of the truss elements

Consideration of partial rotations between beam elements to simulate the lack of sealing of the joints.Reduction of the area and inertia of the beam elements to simulate the effects of cracking and lack of adherence between precast and in situ concrete

Discretization of the deck in truss finite elements with the cables’ axial stiffness (neglecting bending stiffness), adjusting the initial cables tension so as to obtain the measured longitudinal profile after progressive application of the loads

Final model

Model 4

Model 3

Modo nº Freq. medida (Hz) Modelo 1 Freq. (Hz)

Modelo 2 Freq. (Hz)

Modelo 3 Freq. (Hz)

Modelo 4 Freq. (Hz)

Modelo final Freq. (Hz)

1 1.116 0.849 0.794 0.724 1.096 .980 2 2.027 2.448 2.654 0.937 2.442 2.033 3 2.115 1.902 1.822 1.446 3.813 2.250 4 2.483 2.096 2.002 1.547 3.895 2.550 5 - 2.217 7.496 3.651 6 3.815 3.415 3.401 3.376 7.569 4.115 7 4.387 3.782 3.630 3.034 12.4 4.676

FINITE ELEMENT UPDATINGFinal model

Discretization of the deck in truss finite elements, with progressive loading and activation of beam elements. Consideration of partial rotations between beam elements to simulate the lack of sealing of the joints. Reduction of the area and inertia of the beam elements to simulate the effects of cracking and lack of adherence between precast and in situ concrete.

Identified vs calculated mode shapes

-3

-2

-1

0

1

2

0 10 20 30 40 50 60

Freq.=1.116HzNumerical

-3-2-10123

0 10 20 30 40 50 60


-3-2-10123

0 10 20 30 40 50 60


-3

-2

-1

0

1

2

0 10 20 30 40 50 60


-3-2-1012

0 10 20 30 40 50 60

Freq.=3.651Hz

-3-2-10123

0 10 20 30 40 50 60


-3

-2

-1

0

1

2

0 10 20 30 40 50 60


-4

-2

0

2

4

0 10 20 30 40 50 60

Freq.=5.829Hz

Numerical

FINITE ELEMENT UPDATING

FINITE ELEMENT UPDATINGVIBRATION BASED DAMAGE DETECTION

Trends for development• Application of automatic procedures for finite

element updating and damage detection• Development of laboratory tests on beams• Introduction of realistic damage scenarios in an

existing bridge

PEDESTRIAN INDUCED VIBRATIONS

Stainless steel footbridge

TRAFFIC INDUCED VIBRATIONSSYNPEX Project: Advanced Load Models for Synchronous Pedestrian Excitation and Optimized Design Guidelines for Steel Bridges

• Requirements, problems and damages• Pedestrian induced dynamic forces• Mathematical load models for pedestrian induced forces• Measurements in existing footbridges• Numerical simulations• Development of design guidelines and recommendations• Control of vibrations

Workpackages:Partners: RWTH Aachen, FEUP, CTICM, SBP

TRAFFIC INDUCED VIBRATIONS


• Measurement of pedestrian forces• Methods for numerical prediction of maximum levels

of vibration• Design and simulation of control of vibration devices

ROADWAY BRIDGESEXPERIMENTAL ASSESSMENT

Strain gages Load cells Tests

ROADWAY BRIDGES

-0.50

-0.25

0.00

0.25

0.50

0.75

1.00

1.25

5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00

t (s)

εdyn

(t)

/ εst

a

ExperimentalNumerical

DAFexp =1.188DAFnum =1.140

NUMERICAL MODELLING AND VALIDATION

Static and dynamic tests

G 2 G 1

1M 1 , I

3 .6 5 2 .2 0

T ra ile r

T ra c to r

, IM 2 2

2z θ 2 1z

z

M

s 2 j

t 2 j

k s 2 jc

t 2 jk t 2 jc

t 1 j

zr 1 jk

z t 2 j

zr 2 jk

M

s 1 j

t 1 j

k s 1 jc

t 1 jk t1 jc

r 1 jQr 2 jQ

1 .3 5 0 .9 0

RAILWAY BRIDGES


• Structural integrity assessment of old metalic railway bridges (fatigue assessment)

• High speed railway traffic- Dynamic effects in bridges- Vibrations in soils

CABLE VIBRATIONSSTRUCTURAL MONITORING

Cable vibrations at GUADIANA BRIDGE


Damage in stay cables at GUADIANA BRIDGE

• Numerical modelling of the dynamic behaviour of a cable-stayed bridge

• Development of a multi-sensorial distributed instrumentation system

• Experimental characterization of the dynamic behaviour of the bridge

• Test and development of force sensors• Development of video camera for vibration measurements• Development of monitoring software• Laboratory tests of physical models of stay cables• Study of passive and semi-active control solutions

Workpackages:


Cable vibrations in cable-stayed bridgesFCT Project

STRUCTURAL MONITORING


• Robust commercial solution• Innovative solution:

- multi-sensorial distributed instrumentation system- data acquisition with local digitizationand signal conditioning

- single cable transmission- remote control from the lab (GSM or Internet)

CONTROL OF VIBRATIONS


• Control of vibrations in footbridges• Control of vibrations in stay cables• Design and simulation of:

- passive- active- semi-active

solutions

CONCLUSION

MAIN TOPICS FOR JOINT RESEARCH

• Structural Monitoring and Damage Detection in Bridges

• Analysis and Control of Traffic Induced Vibrations in Bridges

new trends in dynamic bridge testing the perspective of … · new trends in dynamic bridge testing...

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