proof load testing of reinforced concrete slab bridges in the netherlands
TRANSCRIPT
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
2
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
3
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
4
Why load testing? (2)
5
Safety philosphy of proof load testing
• Safety philosophy • Stop criteria:
• Further loading not permitted • Failure near • Irreversible damage near
MSc Thesis W. Vos
6
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
7
Existing Guidelines for proof loading
• Europe: DAfStB Richtlinie • Originally derived for
buildings • Plain and reinforced
concrete • For flexure • Structures with large
existing cracking?
8
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
9
Research need
• Guideline for proof loading of existing bridges for the Netherlands
• Flexure + shear
• Measurements? Target proof load?
10
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
11
Heidijk & Medemblik
• Heidijk • RC slab bridge • ASR-damage • Hydraulic jacks (handpump)
and loading frame • Medemblik
• RC girder bridge • Corrosion damage • BELFA
12
Vlijmen-Oost
• Loading: BELFA • Viaduct with ASR • Testing while viaduct was in
service • Measurements:
• Lasers • Acoustic emissions • LVDTs
13
Halvemaans Bridge Alkmaar
• Load application: Mammoet • Flexural capacity • Bridge closed for 1 night • Measurements:
• Lasers • Acoustic emissions • LVDTs
14
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
15
Ruytenschildt Bridge (2)
• Study cracks and deformations for applied loads • Crack formation: acoustic emissions measurements
• Control load process
16
Viaduct Zijlweg
• Loading: Mammoet • Viaduct with ASR • Viaduct closed for 1 week • Measurements:
• Lasers • Acoustic emissions • LVDTs
17
Viaduct de Beek
• Insufficient flexural capacity • Lane restriction
• Limitation:
• Test span 1 • Not above highway • Span 2 is critical
• Assessment requires plastic
redistribution
18
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
19
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
20
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
21
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
22
Execution steps (2)
23
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
24
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
25
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