Challenge the future

Delft University of Technology

Proof load testing

Eva Lantsoght, Cor van der Veen, Ane de Boer, Dick Hordijk

of reinforced concrete slab bridges in the Netherlands

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Overview

• Introduction • Why proof loading? • Existing guidelines?

• Past proof load tests by TU Delft • Recommendations

• Preparation of proof load tests • Execution of proof load tests • Analysis 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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Safety philosphy of proof load testing

• 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 • Different goal from diagnostic

load testing

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Existing Guidelines for proof loading

• Europe: DAfStB Richtlinie • Originally derived for

buildings • Plain and reinforced

concrete • 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: • Proof load testing load

combination • Cyclic loading protocol

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Research need

• Guideline for proof loading of existing bridges for the Netherlands

• Flexure + shear

• Measurements? Target proof load?

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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 Zijlweg 2015 • Viaduct De Beek 2015

Load test to failure of Ruytenschildt Bridge, summer 2014

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Heidijk & Medemblik

• Heidijk • RC slab bridge • ASR-damage • Hydraulic jacks (handpump)

and loading frame • Medemblik

• RC girder bridge • Corrosion damage • BELFA

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Vlijmen-Oost

• Loading: BELFA • Viaduct with ASR • Testing while viaduct was in

service • Measurements:

• Lasers • Acoustic emissions • LVDTs

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Halvemaans Bridge Alkmaar

• Load application: Mammoet • Flexural capacity • Bridge closed for 1 night • Measurements:

• Lasers • Acoustic emissions • LVDTs

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Ruytenschildt Bridge (1)

• Load application: Mammoet • Measurements:

• Lasers • Acoustic emissions (2 teams) • LVDTs

• Sawcut for testing • Testing to failure

• 3049 kN in span 1 • 3991 kN in span 2

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Ruytenschildt Bridge (2)

• Study cracks and deformations for applied loads • Crack formation: acoustic emissions measurements

• Control load process

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Viaduct Zijlweg

• Loading: Mammoet • Viaduct with ASR • Viaduct closed for 1 week • Measurements:

• Lasers • Acoustic emissions • LVDTs

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Viaduct de Beek

• Insufficient flexural capacity • Lane restriction

• Limitation:

• Test span 1 • Not above highway • Span 2 is critical

• Assessment requires plastic

redistribution

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Preparation steps (1)

• Preliminary inspection and rating

• 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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Preparation steps (3)

• Sensor plan: • Deflection profiles in

longitudinal and transverse direction

• Deflection at supports • Strain on bottom of cross-

section • Reference strain

measurements to correct for T • Opening existing cracks • Opening new cracks • Applied load => load cells

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Execution steps (1)

• Cyclic loading scheme • Acoustic emission measurements • Check linearity and reproducibility of measurements • Check residual deformations => no non-linearity • Load levels ≈ safety levels CC3 RBK:

• Low level to check instrumentation • SLS • Intermediate level • Target proof load

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Execution steps (2)

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Analysis Steps (1)

• Data analysis • Correct for T • Correct for support

displacements • Make final plots for report

• Finite element model • Updating • cfr. diagnostic load testing

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Discussion and future research

• Standardize target proof load in Europe

• Load model is not representative of vehicles

• Load factors for proof loading? • Minimum measurements • “Quick and easy” method

for practice

• Draft guidelines submitted to RWS in December

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Summary and conclusions

• Proof loading to approve existing bridges

• Existing guidelines: • Only flexure • Cracked structures?

• Pilot proof load tests in the Netherlands • Current recommendations

• Preparation • Execution • Analysis

• First draft guidelines for practice submitted

Viaduct Zijlweg

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Contact:

Eva Lantsoght

E.O.L.Lantsoght@tudelft.nl // elantsoght@usfq.edu.ec

+31(0)152787449