FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006 DECK-INDUCED STAY CABLE VIBRATIONS: FIELD OBSERVATIONS AND ANALYTICAL MODEL Ming Ming - - Yi Liu Yi Liu Sinotech Engineering Consultants, Inc., Taipei, Taiwan Delong Zuo Johns Hopkins University, Baltimore, MD, USA Nicholas P. Jones Johns Hopkins University, Baltimore, MD, USA
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DECK-INDUCED STAY CABLE VIBRATIONS: FIELD ... Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006 DECK-INDUCED STAY CABLE VIBRATIONS: FIELD OBSERVATIONS AND ANALYTICAL MODEL
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FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006
DECK-INDUCED STAY CABLE VIBRATIONS: FIELD OBSERVATIONS AND ANALYTICAL MODEL
Delong ZuoJohns Hopkins University, Baltimore, MD, USA
Nicholas P. JonesJohns Hopkins University, Baltimore, MD, USA
FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006
Finite element modelingFinite element modeling
Field observationsField observations
Analytical modelingAnalytical modeling
ScopeScope
FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006
The Fred Hartman BridgeThe Fred Hartman BridgeOver the Houston ship channel in Houston, Texas, USAOver the Houston ship channel in Houston, Texas, USA384 m main span, 54 m clearance384 m main span, 54 m clearanceTwinTwin--deck, each 24 m wide and 2.87 m highdeck, each 24 m wide and 2.87 m highDoubleDouble--diamond shaped towers diamond shaped towers 192 cables (59 m to 198 m long) in four inclined planes192 cables (59 m to 198 m long) in four inclined planes
FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006
FullFull--Scale Measurement SystemScale Measurement System
South Tower North Tower
AS13-AS24 AS1-AS12 AN24-AN13 AN12-AN1
Major measurementMajor measurementStaysStays
AccelerationAccelerationDisplacementDisplacementDamper forceDamper force
Sampling rate = 40 HzSampling rate = 40 HzLowLow--pass filtered at 10 Hzpass filtered at 10 HzFiveFive--minute recordsminute records
Veering of naturalVeering of naturalfrequency locifrequency loci
CoupledCoupled
GlobalGlobal
LocalLocal
Pure cable frequencyPure cable frequency
FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006
Global MotionsGlobal MotionsOECSf1 = 0.2902 Hz
xz
yMode 1
MECS
xz
y
f1 = 0.2919 Hz
Mode 1
OECS
xz
y
f2 = 0.3004 Hz
Mode 2
MECS
xz
y
f2 = 0.3021 Hz
Mode 2
FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006
Local MotionsLocal Motions
xz
y
f15 = 0.5825 Hz
Mode 15
MECS
xz
y
f16 = 0.5825 Hz
Mode 16
MECS
xz
y
f19 = 0.5825 Hz
Mode 19
MECS
xz
y
f20 = 0.5825 Hz
Mode 20
MECS
FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006
Coupled MotionsCoupled Motions
xz
y
f7 = 0.5468 Hz
Mode 7
MECS
xz
y
f23 = 0.5911 Hz
Mode 23
MECS
xz
y
f8 = 0.5599 Hz
Mode 8
MECS
xz
y
f24 = 0.5954 Hz
Mode 24
MECS
FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006
SummarySummary
L
x HH
k
y(x,t)
μm
qp++
?
OECS OECS ++ CableCable--deck system deck system MECSMECS?
FHWA Cable Stay Bridge Workshop, St. Louis, MO, April 25-27, 2006
LargeLarge--amplitude stay cable vibration induced by deck oscillation have amplitude stay cable vibration induced by deck oscillation have been been observed in the fieldobserved in the field
Analytical modeling revealed that coupled motions of deck and stAnalytical modeling revealed that coupled motions of deck and stay cables are ay cables are associated with the veering associated with the veering of of natural frequency locinatural frequency loci
ThreeThree--dimensional finite element models verified that coupled motion adimensional finite element models verified that coupled motion and nd natural frequency curve veering are exhibited in real structuresnatural frequency curve veering are exhibited in real structures
AAn OECS model with linear vibration theorn OECS model with linear vibration theoryy forfor a cable based on the presented a cable based on the presented model would reasonably evaluate coupled motions model would reasonably evaluate coupled motions forfor engineering applicationsengineering applications, , offering a more efficient approach than a MECS modeloffering a more efficient approach than a MECS model