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Recommendations for proof load testing of reinforced concrete slab bridges - poster


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Proof loading of existing bridges is an option to study the capacity when crucial information about
the structure is lacking. To define the loading criteria for proof load testing, a review of the
literature has been made, finite element models of existing viaducts have been made, and on
these viaducts, proof loading tests have been carried out. These bridges were heavily
instrumented, to learn as much as possible about the structural behaviour during proof loading.
Additional laboratory experiments have been used to develop controlled loading protocols, and to
identify which stop criteria can be used for which case. As a result of the analysis and experiments,
recommendations are given for proof loading of bridges with respect to the required maximum
load and the stop criteria. These recommendations have resulted in a guideline for proof loading
of existing reinforced concrete slab bridges for The Netherlands.

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Recommendations for proof load testing of reinforced concrete slab bridges - poster

  1. 1. Recommendations for proof load testing of reinforced concrete slab bridges Eva O.L. Lantsoght1,2, Cor van der Veen2, Ane de Boer3, Dick Hordijk2 1 Politécnico, Universidad San Francisco de Quito, Quito, Ecuador 2 Concrete Structures, Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands 3 Rijkswaterstaat, Ministry of Infrastructure and the Environment, The Netherlands Proof load testing in the Netherlands To explore the possibility of using proof load testing for the assessment of existing bridges, a number of pilot proof load tests on shear- and flexure-critical bridges, with and without material degradation, were carried out [2]. What is proof load testing? In a proof load test, a load representative of the factored live load is applied to the bridge. If the structure can withstand the applied load without signs of distress, it is experimentally shown that the bridge fulfills the loading requirements. Why proof load testing? Existing bridges often do not rate sufficiently for the current live load models [1]. When uncertainties with regard to material degradation or the structural system are large, proof load testing can be used. Fig. 1: Load application methods (a) Assessment after proof load test Direct result Post-processing of data for report Execution of proof load test Loading protocol Stop criteria Preparation of proof load test Target proof load Load position • Live load: NEN-EN 1991-2:2003 [3] • Different load levels, depending on different safety levels • Using a linear finite element model: find load and load configuration that results in the same sectional shear or sectional moment as Eurocode live loads • For bending moment based on moving the live load to find the position that results in the highest section moment • For shear (RC slab bridges): 2.5d from the face of the support Fig. 2: Moving the live load to find the critical position Fig. 3: Recommended loading protocol Existing flexural cracks? Uncracked Cracked Flexure εc < 0.8 ‰ – εc0 wmax ≤ 0.5 mm wres ≤ 0.1 mm wres < 0.3wmax ΔEI ≤ 25 % Deformation profiles Load-deflection graph εc < 0.8 ‰ – εc0 wmax ≤ 0.5 mm wres ≤ 0.1 mm wres < 0.2wmax ΔEI ≤ 5 % Deformation profiles Load-deflection graph Shear εc < 0.8 ‰ – εc0 wmax ≤ 0.3 mm ΔEI ≤ 5 % Deformation profiles Load-deflection graph εc < 0.8 ‰ – εc0 ΔEI ≤ 5 % Deformation profiles Load-deflection graph • Cyclic loading protocol: check linearity and reproducibility of the measurements • First load level: check all sensors • Second load level: Serviceability Limit State • Interim level • Target load level as determined with linear finite element analysis • After Serviceability Limit State: small steps for safe loading • Constant loading speed: 3 kN/s – 10 kN/s • Baseline load level to keep jacks and instrumentation activated • Stop criteria based on ACI 437.2M-13 [4] and DAfStB [5] • Analysis of beams tested in the lab [6] and verification of pilot proof load tests [7] • Note: limited data of lab tests on shear • Future work: improvement of stop criteria for shear and verify with experiments on slabs References [1] Lantsoght EOL, van der Veen C, de Boer A, Walraven JC (2013) Recommendations for the Shear Assessment of Reinforced Concrete Slab Bridges from Experiments. Structural Engineering International, Vol. 23, Nr. 4, pp. 418-426 [2] Lantsoght EOL, Van der Veen C, De Boer A, Hordijk DA (in press) Proof load testing of reinforced concrete slab bridges in the Netherlands. Structural Concrete. [3] CEN, Eurocode 1: Actions on structures - Part 2: Traffic loads on bridges, NEN-EN 1991-2:2003. 2003, Comité Européen de Normalisation: Brussels, Belgium. p. 168. [4] ACI Committee 437, Code Requirements for Load Testing of Existing Concrete Structures (ACI 437.2M-13) and Commentary 2013: Farmington Hills, MA. p. 24. [5] Deutscher Ausschuss für Stahlbeton, DAfStb-Guideline: Load tests on concrete structures (in German). 2000, Deutscher Ausschuss fur Stahlbeton,. p. 7. [6] Lantsoght EOL, Yang Y, van der Veen C, de Boer A, Hordijk DA (2017) Beam experiments on acceptance criteria for bridge load tests. ACI Structural Journal Vol. 114, Nr. 4, pp. 1031-1041. [7] Lantsoght, E., Verification of stop critera for proof load tests. 2017, Delft University of Technology: Delft. p. 40. Table 1: Overview of stop criteria Fig. 5: Beam test and instrumentation used for verification of stop criteria • Correction of measurements for deflection of support • Correction of measurements for effects of temperature and humidity Fig. 4: Envelope of load- deflection graph for pilot proof load test De Beek: (a) bending moment; (b) shear