defining loading criteria for proof loading

Challenge the future

DelftUniversity ofTechnology

Defining loading criteria for proof loading

Rutger Koekkoek, Eva Lantsoght, Yuguang Yang, Ane de Boer, Dick Hordijk

of existing reinforced concrete bridges

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Overview• Introduction• Why proof loading?• Stop criteria?

• Overview of existing guidelines• Past proof load tests by TU Delft• Recommendations• Preparation of proof load tests• Execution of proof load tests

• Summary and conclusions Slab shear experiments, TU Delft

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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

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Why load testing? (2)

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Stop criteria

• Safety philosophy• Stop criteria:• Further loading not permitted• Failure near• Irreversible damage near

MSc Thesis W. Vos

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Proof load testing of bridges

• Apply predetermined load to bridge• Information lacking• Damage due to ASR, …

• Proof load testing• Immediate approval of

bridge• Recalculate updated β

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Existing Guidelines for proof loading

• Europe: DAfStB Richtlinie• Stop criteria• Concrete strain• Steel strain• Crack width and residual

crack width (new & existing cracks)• Residual deflection

• For flexure• Structures with large

existing cracking?

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Existing Guidelines for proof loading

• North America: • Buildings: ACI 437.2M-

13• Bridges: Manual of

Bridge Rating Through Load Testing (1998)

• ACI 437.2M-13 stop criteria:• Residual deflection• Permanency ratio• Deviation from Linearity

Index

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Research need

• Guideline for proof loading of existing bridges for the Netherlands

• Flexure + shear• Stop criteria?

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TU Delft Proof Load Tests

• Proof load tests:• Heidijk 2007• Medemblik 2009• Vlijmen-Oost 2013• Halvemaans Bridge 2014• Ruytenschildt Bridge 2014• Viaduct in the Zijlweg 2015• Viaduct De Beek 2015

Load test to failure of Ruytenschildt Bridge, summer 2014

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Preparation steps (1)

• Determination of dimensions

• Live load: EN 1991-2:2003

• RBK load levels• Different β• Different load factors

• In FEM model• mx over 3 m• v over 4d

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Preparation steps (2)

• Critical position• Bending moment: largest

moment• Shear: 2.5d from support

• Required proof load• Same shear or bending

moment as with load combination• Value → considered

safety level

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Execution steps

• Cyclic loading scheme• Acoustic emission measurements• Check linearity and reproducibility of measurements• Check residual deformations

• Stop criteria• Evaluated during tests• Research in progress• Criteria for shear failure need to be developed

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Summary and conclusions

• Proof loading to approve existing bridges

• Existing guidelines: • Only flexure• Cracked structures?

• Determination of maximum proof load• LFEA• Different safety levels

• Execution• Cyclic loading protocol• Safely applying large loads

Viaduct Zijlweg, tested in summer 2015

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Contact:Eva LantsoghtE.O.L.Lantsoght@tudelft.nl // elantsoght@usfq.edu.ec+31(0)152787449