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Challenge the future
DelftUniversity ofTechnology
Determination of loading protocol and stop
criteria for proof loading with beam tests
Eva Lantsoght, Yuguang Yang, Cor van der Veen, Ane de Boer, Dick Hordijk
2Determination of loading protocol and stop criteria for proof loading with beam tests
Overview
• Introduction• Why proof loading?
• Stop criteria?
• Overview of existing guidelines• Lab experiments• Results• Recommendations• Summary and conclusions
Slab shear experiments, TU Delft
3Determination of loading protocol and stop criteria for proof loading with beam tests
Why load testing? (1)
Bridges from 60s and 70s
The Hague in 1959
Increased live loads
common heavy and long truck (600 kN)
End of service life + larger loads
4Determination of loading protocol and stop criteria for proof loading with beam tests
Elements for load testing
• Target load• Loading protocol• Stop criteria:
• Further loading not permitted
• Failure near
• Irreversible damage near
MSc Thesis W. Vos
5Determination of loading protocol and stop criteria for proof loading with beam tests
Existing Guidelines for proof loading
• DAfStB Stop criteria for flexure• Concrete strain
• Steel strain
• Crack width and residual crack
width
• Residual deflection
• ACI 437.2M-13 Acceptancecriteria for flexure:• Residual deflection
• Permanency ratio
• Deviation from Linearity Index
• No stop criteria for shear
6Determination of loading protocol and stop criteria for proof loading with beam tests
Research need
•Stop criteria for flexure and shear
•Loading protocol for field testing
7Determination of loading protocol and stop criteria for proof loading with beam tests
Experiments (1)
• Beams P804 and P502 cast in lab: plain bars• Cyclic loading protocol
• Number of cycles
• Loading speed
• Tests: Failure in shear and flexure
• Measurements:
• Lasers: deflection of beam
• LVDTs: crack opening + horizontal deformation
• Acoustic emission sensors in shear span
Flexural failure, P804A1
Shear failure, P804A2
8Determination of loading protocol and stop criteria for proof loading with beam tests
Experiments (2)
Test a
(mm)
dl
(mm)
fcm
(MPa)
Pshear
(kN)
Pmoment
(kN)
Ppred
(kN)
FMpred Pu
(kN)
FM
P804A1 3000 755 63.5 273 199 199 F 207 F
P804A2 2500 755 63.5 219 248 219 S 232 S
P804B 2500 755 63.5 219 248 219 S 196 S
P502A2 1000 465 71.5 150 154 150 S/F 150 F
9Determination of loading protocol and stop criteria for proof loading with beam tests
Experiments (3)
P804A1 P804A2
P804B P502A2
10Determination of loading protocol and stop criteria for proof loading with beam tests
Recommendations (1)
• Cyclic loading protocol• Constant loading speed• Four load levels• After SLS: use small steps to go to interim and target level
11Determination of loading protocol and stop criteria for proof loading with beam tests
Recommendations (2)
Existing flexural cracks?
Failure mechanism Uncracked Cracked
Flexural failure εc < 0.8 ‰ – εc0
wmax ≤ 0.5 mm
wres ≤ 0.1 mm
wres < 0.3wmax
Stiffness reduction ≤ 25 %
Deformation profiles
Load-displacement graph
εc < 0.8 ‰ – εc0
wmax ≤ 0.3 mm
wres ≤ 0.1 mm
wres < 0.2wmax
Stiffness reduction ≤ 5 %
Deformation profiles
Load-displacement graph
Shear failure εc < 0.8 ‰ – εc0
wmax ≤ 0.3 mm
Stiffness reduction ≤ 5 %
Deformation profiles
Load-displacement graph
εc < 0.8 ‰ – εc0
Stiffness reduction ≤ 5 %
Deformation profiles
Load-displacement graph
12Determination of loading protocol and stop criteria for proof loading with beam tests
Summary and conclusions
• Proof loading to approve existingbridges
• Existing guidelines: • Only flexure
• Precracked structures?
• Laboratory testing• Loading protocol
• Cyclic, constant loading speed
• Proposal with 4 levels
• Stop criteria• Based on ACI and DAfStB
• Effect of cracking
• Difference between flexure and shear
Viaduct Zijlweg, tested in summer 2015
13Determination of loading protocol and stop criteria for proof loading with beam tests
Contact:
Eva Lantsoght
[email protected] // [email protected]
+31(0)152787449
