6/18/2013 1 End Region Detailing of Pretensioned Concrete Bridge Girders End Region Detailing of Pretensioned Concrete Bridge Girders Trey Hamilton, PE, PhD, Univ. of Florida Brandon E. Ross, PE, PhD, Clemson Univ. Technical Coordinator: Sam Fallaha, PE FDOT Contract BDK75 977-05 2 of 57 Presentation Outline Prestressing basics Background on end region reinforcement FIB54 Test Program – Service and Ultimate FIB63 Test Program – Service Findings
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6/18/2013
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End Region Detailing of Pretensioned Concrete Bridge Girders
End Region Detailing of Pretensioned Concrete Bridge Girders
Trey Hamilton, PE, PhD, Univ. of FloridaBrandon E. Ross, PE, PhD, Clemson Univ.
Technical Coordinator: Sam Fallaha, PEFDOT Contract BDK75 977-05
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Presentation Outline
Prestressing basics
Background on end region reinforcement
FIB54 Test Program – Service and Ultimate
FIB63 Test Program – Service
Findings
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End Region
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Effect of Prestressing
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Prestressing-Hoyer Effect
Flame-cut
Unstressed strand expands back to original diameter
Girder
strand
Girder
strand
Concrete restrains expansion of strandResult: tension stress
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Prestressing-Transfer Length
Transfer Length (60ds)
TendonForce
Effective prestress force in tendon
Tendon FBD
Girder FBD
Bond Stress
Bond Stress
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Prestressing-Transfer Length
Transfer Length (60ds)
TendonForce
Effective prestress force in tendon
Tendon FBD
Girder FBD
Bond Stress
Bond Stress
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Prestressing Effect-Splitting
ez
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Splitting-Web
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Splitting-Flange
Z
X
Tadros et al. (2010)
exX
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Prestressing Effect-Partial Debonding
Excerpt:
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Ultimate Strength-Strut and Tie
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Ultimate strength-Strut and Tie
ConsiderationsFactored Load
Flange GeometryBearing
GeometryStrand Locations
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Lateral-Splitting Failure
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LRFD “Confinement”
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FDOT Standard Details
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Research Approach
FIB54: Flange Cracks & Ultimate CapacityFIB63: Web Cracks
Finite Element Analysis
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FIB54 10 Specimens (5 beams)
Fabrication Strain data Crack data
Load tests Behavior Capacity
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FIB54 Reinforcement and Prestressing Scheme
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FIB54 Reinforcement and Prestressing Scheme
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FDOT Confinement
Modified Confinement No Confinement (2)
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No Bearing Plate
Bearing Plate
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FIB54 Debonding
45% debonded
13% debonded
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FIB54-ResultsFlange Splitting Cracks
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44.0
99.0
219.5
134.0
104.0
41.5
107.0
0
50
100
150
200
250
Tota
l len
gth
(in.)
Length of flange-splitting cracks
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Analytical Program
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FEA + Experimental-Transfer Length
Stage 1 – outer strands released Stage 2 – all strands released
End Region Detailing of Pretensioned Concrete Bridge Girders
Available on theFDOT Research Website
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Thank You Experimental work conducted at
M. H. Ansley Structures Research Center Many thanks to Sam Fallaha and the Center’s
staff! David Allen Adam Brennan Frank Cobb Steve Eudy Tony Hobbs Will Potter Paul Tighe David Wagner Chris Weigly Steven Nolan, P.E., FDOT Structures Design Office