Field Monitoring and Numerical Simulation for Performance ......ThermalNeg HL 93 EXP HL 93 CON Pure...
Transcript of Field Monitoring and Numerical Simulation for Performance ......ThermalNeg HL 93 EXP HL 93 CON Pure...
Field Monitoring and Numerical Simulation for Performance Assessment of Integral Abutment Bridges
James M. LaFave, PhD, PEProfessor and CEE Excellence Faculty ScholarAssociate Head & Director of Undergraduate StudiesDepartment of Civil & Environmental Engineering (CEE)University of Illinois at Urbana-Champaign (UIUC) Transportation & Highway
Engineering (T.H.E.) Conference February 27th, 2018
Outline 2
Introduction – Integral Abutment Bridges (IABs)
IAB Parametric Study – Numerical Simulations Overview of modeling methodology Summary of analytical modeling results
IAB Field Monitoring of Two Highway Bridges Implementation of field monitoring systems Summary of field data
Ongoing Work
Integral Abutment Bridges (IABs)3
IABs can provide benefits in terms of decreased construction and maintenance costs
The superstructure & substructure acts as one continuous unit under thermal & other post-construction loading
Most previous IAB research has focused on substructure behavior & demand
Typical Integral Abutment Detail (IDOT Bridge Manual, 2012)
Abutment
Substructure
Superstructure
IABs in Illinois4
IDOT IAB design & construction limits have been placed on highway bridge length & skew configurations Mainly a function of pile type, based on substructure considerations
Previous research in Illinois has investigated soil-pile interaction at IAB foundations
UIUC CEE IAB Research5
Research Goals: Gain a better understanding of IAB behavior (particularly under
thermal loads and for superstructures) Improve the design and construction provisions for IDOT IABs
Two-Part Research Project: Detailed parametric study employing finite element models of
IABs Instrumentation & field monitoring of two (2) IABs in northern
Illinois
IAB Parametric Study – Numerical Simulations6
Typical IAB SAP Analytical Model
Deck and Pier: Shell elements
Girders and Piles: Frame elements
Abutments: Shell elements
Soil and Abutment Backfill:Nonlinear elastic springs
(Soil springs obtained using LPILE)
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Nonlinear Pile Behavior:Fiber hinge elements (top 5 ft)
IAB Modeling – Primary Parameters8
Primary Parameters Are Largely Based Around Bridge Geometry:
Number of spans (1 to 20) Individual span lengths (50, 100, 150 & 200 ft) & end-span ratio Overall length (up to 1200 ft) Skew (0, 15, 30, 45 & 60 degrees) Width (36, 60 & 96 ft) Piles (HP8 HP18)
Global Movement vs. Effective Expansion Length9
Increasing EEL results in an increase in global longitudinal movement
The resulting model displacements are typically more than 90% of those corresponding to free expansion / contraction
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‐1
0
1
2
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5
0 100 200 300 400 500 600 700Long
itudina
l Displacem
ent (in.)
EEL (ft)
Dead
HL‐93
PosThermal
NegThermal
Free Expansion
Global Movement with Skew10
Increased bridge skew results in non-symmetric movement of the acute and obtuse corners Bridges with skew between 0° and 30° exhibit more symmetric movement For skews above 30°, movement is toward the acute corner
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0
100
200
300
400
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-1000 0 1000 2000 3000 4000 5000
y-co
ordi
nate
(in)
x-coordinate (in)
150' x 2 HP14x117 45° Skew Bridge
Undeformed Deformed -80 Deformed +80
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0
100
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y-co
ordi
nate
(in)
X-coordinate (in)
150' x 2 HP14x117 0° Skew Bridge
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0 500 1000 1500 2000 2500 3000 3500 4000
Botto
m S
tres
s (k
si)
Length along bridge, in.
Bottom Flange Stress in 3-Span IAB w/ HP14x73
Dead Staged HL 93 Thermal
ThermalNeg HL 93 EXP HL 93 CON
Pure Thermal Pure ThermalNeg
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0 500 1000 1500 2000 2500 3000 3500 4000
Botto
m S
tres
s (k
si)
Length along bridge, in.
Bottom Flange Stress in 3-Span IAB w/ HP14x73
Pure Thermal Pure ThermalNeg
Thermally-Induced Girder Stresses11
Girder Section: W36x194
Girder bottom stress values control for composite sections
Maximum stresses due only to thermal load are located at the abutments
Girder Bottom Stress with Skew12
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0 50 100 150 200 250 300 350 400 450
Bottom
stress (k
si)
y‐coordinate (in., obtuse ‐> acute girder)
4 – 100’ spans & HP14x73 (Pure Positive Thermal)
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0 50 100 150 200 250 300 350 400 450
Bottom
Stress (ksi)
y‐coordinate (in., obtuse ‐> acute girder)
4 – 100’ spans & HP14x73 & HL‐93EXP (Dead + Pos. Therm. + Live)
0Skew
15Skew
Pile Strains vs. Skew and EEL13
4x100 ft, HP14x73, EEL = 200 ft 100 ft Spans, HP14x73
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0.002
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0.006
0.008
0.01
0.012
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0 50 100 150 200 250 300 350
Total Strain
EEL (ft)
Max Total Strains (Pure Positive Thermal)
0 Skew
15Skew30Skew45Skew
0
0.001
0.002
0.003
0.004
0.005
0.006
0 1 2 3 4 5 6 7
Strain
Pile Number (obtuse ‐> acute pile)
Pile Peak Strain (Pure Positive Thermal)
Yield
0 Skew
15 Skew
30 Skew
45 Skew
60 Skew
General Effects of IAB Parameters14
Increase in: Effect:
EEL Increase in pile & girder demands
Pile size Decrease in pile demands, increase in girder demands
Bridge skew Increase in pile demands, decrease in girder demands
Bridge width Small increase in pile demands
End-span ratio Decrease in pile & girder demands
IAB Modeling – Secondary Parameters
Soil Foundation Stiffness Default: medium clay Variations: stiff and soft clay, dense and loose sand
Backfill Stiffness Default: uncompacted sand Variations: stiff backfill
Pile Conditions Default: H-piles, weak-axis orientation Variations: pipe piles, H-pile w/ strong-axis orientation, double H-piles
Pile-Top Relief
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Secondary Parameters16
Pile strains increase with: Dense Sand Stiff Clay
Pile strains decrease with: Pipe Piles Pile Relief Loose Sand Soft Clay Stiff Backfill Double Piles Strong-Axis 0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
0.004
0.0045
0 50 100 150 200 250 300 350
Tota
l Str
ain
EEL (ft)
Pile Strains (Pure Thermal)
Default
YIELD
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0 50 100 150 200 250 300 350
Tota
l Str
ain
EEL (ft)
Pile Strains (Pure Thermal)
Default
Clay (Stiff)
Sand (Dense)
YIELD
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0 50 100 150 200 250 300 350
Tota
l Str
ain
EEL (ft)
Pile Strains (Pure Thermal)
Default
Clay (Stiff)
Clay (soft)
Stiff Backfill
Double Piles
Strong Axis
Pile Relief
Pipe16x0.312
Pipe16x0.375
Sand (Dense)
Sand (Loose)
YIELD
Outcomes for Design17
Pile strain and girder stress nonlinear regressions:
0 0.5 1 1.5 2 2.5 3 3.5 40
5
10
15
20
25
30
35
40
Girder Stress Influence Coefficient, girder
Gird
er S
tress
(ksi
)
All Skews, R2 = 0.9229
ObservedPredicted
0200400600800
100012001400160018002000
0 20 40 60EE
L (f
t)Abutment Skew (degrees)
Pile Chart (HP14x117, D+Th+L, 5x Yield)
200 ft spans
150 ft spans
100 ft spans
50 ft spans
IDOT Pile Chart
Proposed updated pile charts:
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IAB Field Monitoring of Two Highway Bridges19
IAB Instrumentation Goals20
Measuring strain in the concrete deck & steel girders
Checking level of embedded girder fixity
Checking for differential tilt at abutment joint
Measuring strain at pile-abutment interface
Monitoring bridge movement at various joints
Monitoring behavior of the approach slab
Bridge Instrumentation Schematics
EB I-90 Kishwaukee River
Bridge
EB I-90 Union Pacific Railroad (UPRR) Bridge
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• 4-Span• 549 ft• 30° Skew• HLMR Guided Expansion Bearing @ Exp. Pier
• Single-Span• 184.5 ft• 42.5° Skew
Kishwaukee Bridge Instrumentation Details (similar scheme for UPRR)
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Modeling of Site Bridges
SAP2000 was also used to model each instrumented bridge
Boring logs were utilized to determine backfill and foundation soil properties at each site
Soil softening was included to represent pile-top relief: Kishwaukee Bentonite slurry UPRR MSE wall effects
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Displacements – Kishwaukee 24
Approach Slab Behavior25
Strains are not uniform throughout the approach slab
Average strain indicates a clear trend with change in temperature
Abutment Cold Joint Rotations 26
Middle band = 74% of data Middle band = 86% of data
UPRR Kishwaukee
Girder Differential Rotations27
Middle band = 68% of dataMax rotation: 0.33°
Middle band = 49% of data Max rotation: 0.1°
UPRR Kishwaukee
Kishwaukee Field vs. Model Abutment Rotations28
Pile Strains29
Pile top strains from the field data are closer to pure weak-axis flexure than combined flexure
Strong-axis bending causes a separation in magnitude between strain gage pairs
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42
bf/4
Bridge
Axial force causes a shift in the magnitude of tensile vs. compressive strain
Kishwaukee – Obtuse Pile Top Strains
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Axial contribution causes upward shift in magnitude; strong-axis bending causes a separation between gage pairs
Girder Demands
Top-flange and web gages trend well over time and with temperature Bottom-flange measurements typically deviate from expected trends over
time, after the first fall/winter/spring
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T
B
bf/4
M
Seasonal Girder Stresses
After the first year of data collection, bottom-flange stresses deviate from model predictions, while top-flange stresses stay similar as before
The highest girder stresses are seen near the abutments:
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Overall Conclusions for IABs34
IAB Analysis (Parametric Study) Bridge expansion & contraction are about 90% of the magnitude of free
expansion & contraction Thermally-induced stresses in the superstructure should be considered when
proportioning girders (especially in end-spans) An allowance for moderate inelastic deformation in pile foundations may
broaden the range of acceptable bridge layouts
IAB Instrumentation (Field Monitoring) Field results were used to validate parametric study analytical models and to
better understand IAB & approach slab performance Pile strains in the field closely follow predicted analytical trends Girder bottom flanges exhibit the highest thermal stress ranges
Ongoing Work – IAB Approach Slab Research35
Research Goals: Identify the fundamental cause of cracking
issues in IAB approach slabs Develop improved design criteria and
procedures to mitigate cracking
Three Main Components: Investigation of existing IAB approach
slabs Numerical modeling parametric study Field instrumentation & monitoring of two
Illinois Tollway IAB approach slabs
Approach slab embedded strain gage instrumentation
Initial Approach Slab Model
IAB Seismic Research 36
Research Goals: Assess the behavior of IABs
to a 1000-year return period seismic event
Form recommendations to improve seismic design & construction of IABs, with a focus on southern Illinois
Two Main Components: Develop 1000-year return
period hazard ground motions for southern Illinois
Model IABs in OpenSees and assess their seismic behavior
Ground motions developed for Cairo, IL
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Period, T (sec)S
pect
ral A
ccel
erat
ion,
Sa (g
)
Mean
Schematic of the three‐span IAB used for modeling in OpenSees
0 20 40 60 80 100Time (s)
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Tota
l Tra
nsve
rse
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e S
hear
(N)
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Total base shear in a three-span steel IAB during a ground motion
Acknowledgements37
Illinois Department of Transportation (IDOT)
Illinois Tollway
Illinois Center for Transportation (ICT)
ICT R27-115 Technical Review Panel – Chair: Mark Shaffer (IDOT)
Co-PI & UIUC CEE Professor Larry Fahnestock
Gabriela Brambila, Joseph Riddle, Matthew Jarrett, Jeffrey Svatora, Beth Wright & Huayu An (former UIUC CEE Graduate Student Researchers)