Dick A. Hordijk

Collapse test and moment capacity of the Ruytenschildt reinforced concrete slab bridge

Abstract A large number of existing reinforced concrete solid slab bridges in the Netherlands are found to be insufficient for shear upon assessment. However, research has shown additional sources of capacity in slab bridges, increasing their total capacity and possibly changing their failure mode. Previous testing was limited to half-scale slab specimens cast in the laboratory. To study the full structural behaviour of slab bridges, testing to failure of a bridge is necessary. Research on load testing is carried out in order to develop load testing guidelines. In August 2014, a bridge was tested in two spans. The bridge was load tested, and additional cycles until yielding occurred in the reinforcement were added to the experiment. Though calculations with current design provisions showed that the bridge could fail in shear, the field test showed failure in flexure before shear. The unity check for flexure was determined. The experiment shows that the methods for rating of existing reinforced concrete slab bridges are conservative.

Probabilistic prediction of the failure mode of the Ruytenschildt Bridge

In the Netherlands, the shear capacity of a large number of existing reinforced concrete solid slab bridges is subject to discussion, as initial assessments indicated that their capacity was insufficient. In certain cases, the deterministic value of the moment capacity is larger than the deterministic value of the shear capacity. However, when the variability of the material properties, and of the capacity models themselves are factored in, a probability of a certain failure mode can be calculated. Here, a method is introduced to calculate the chance that a cross-section fails in shear before it fails in bending. The method that is derived here is applied to the Ruytenschildt Bridge. This case study is a reinforced concrete solid slab bridges that was tested to failure in two spans during the summer of 2014. The relative probability of failure in shear of the bridge was determined. The predictions indicated a smaller probability of a shear failure than of a bending moment failure. In the first tested span, failure was not reached, but indications of flexural distress were observed. In the second span, a flexural failure was achieved, in line with the probabilistic predictions. The presented method can be used in the assessment of existing bridges to determine which failure mode is most probable, taking into account the variability of materials and capacity models.

Beam Experiments on Acceptance Criteria for Bridge Load Tests

Loading protocols and acceptance criteria are available in the literature for load tests on buildings. For bridges, proof load tests are interesting when crucial information about the structure is missing, or when the uncertainties about the structural response are large. The acceptance criteria can then be applied to evaluate if further loading is acceptable, or could lead to permanent damage to the structure. To develop loading protocols and acceptance criteria for proof loading of reinforced concrete bridges, beam experiments were analyzed. In these experiments, different loading speeds, constant load level times, numbers of loading cycles, and required number of load levels were evaluated. The result of these experiments is the development of a standard loading protocol for the proof loading of reinforced concrete bridges. Based on these limited test results, recommendations for acceptance criteria are also proposed.

Pilot Proof-Load Test on Viaduct De Beek: Case Study

For existing bridges, proof-load testing can be a suitable assessment method. This paper addresses the evaluation of a posted reinforced concrete slab bridge over a highway through proof-load testing, detailing the preparation, execution, and analysis of the test. As the target proof-load and the required measurements for proof-load testing currently are not well-defined in the existing codes, this pilot case was used to develop and evaluate proposed recommendations for proof-load testing for a future guideline on proof-load testing for the Netherlands. Moreover, the pilot proof-load test is used to study the feasibility of proof-load testing for both shear and flexure

Towards standardisation of proof load testing: pilot test on viaduct Zijlweg

Abstract Proof load tests of bridges can be very useful for structures with a lack of information, or for structures of which the effect of material degradation is difficult to assess. Contrary to diagnostic load testing, proof load testing is not well-defined in current standards in terms of required load and analysis of measurements. The risk related to the high loads used in proof load testing requires standardisation for these tests. The paper highlights important considerations for proof load testing that may lead to the development of guidelines in the Netherlands, by illustrating a pilot study on the viaduct Zijlweg in the Netherlands. This reinforced concrete bridge rates too low in shear. Topics of interest are the required load that the bridge has to withstand to be approved by the load test and the interpretation of the measurements during the test to avoid permanent damage to the structure. These measurements were compared to the stop criteria from existing codes for buildings, to examine if recommendations for the use with bridges can be formulated. The final result of the test on this case study is that the capacity of the viaduct is proven to be sufficient for shear and bending moment.

An Experimental Study on the Transition of Failure Between Flexural and Shear for RC Beams

The paper presents a large experimental research program carried out at Delft University of Technology supported by the Dutch Ministry of Infrastructure and the Environment. The research evaluates the shear capacity of RC beam/slab strips at transition of the failure modes between flexural and shear (defined as v bd ). With 106 tests, the values of v bd were obtained for specimens with 7 different configurations covering the variables that are usually found in the existing solid bridge deck slabs. The results are compared with the related expressions suggested by several available design provisions. Suggestions are made to further improve these expressions.

Determination of Loading Protocol and Stop Criteria for Proof Loading with Beam Tests

Proof loading of existing bridges is an interesting option when insufficient information about a bridge is available. To safely carry out a proof loading test, high loads are placed on the bridge. To avoid permanent damage to the structure, a controlled loading protocol needs to be described, and the measurements need to be closely monitored to identify the onset of distress. The criteria from existing codes and guidelines to evaluate the measurements, called stop criteria, are not universally applicable. To develop recommendations for proof loading of reinforced concrete solid slab bridges, beam experiments were analysed. The beams were heavily instrumented to evaluate the existing stop criteria, and possibly develop new stop criteria. The result of these experiments is the development of a standard loading protocol for the proof loading of reinforced concrete slab bridges. Recommendations for the use of the stop criteria are also formulated. These insights are used to develop a new guideline for the proof loading of reinforced concrete slab bridges in the Netherlands.

Suitability of Shear Tension Code Requirements for the Assessment of Existing Structures Build-Up with Prestressed I- and T-Shape Girders

For existing structures, it is of interest to know if codes are conservative. If this is the case, it can be useful to examine if more accurate assessment methods are feasible. This paper addresses this topic for shear tension code requirements. Shear tension failure is of importance for prestressed structures with thin webs such as I- T- and Box girder structures. The studied codes are the fib Model Code (2010) (MC2010), the ACI building codes (ACI) and Eurocode 2 (EC2). These code requirements are based on the concept that the principle tensile stresses are limited to the concrete tensile strength. For that reason the resistance to web shear cracking is studied in this paper. To examine the suitability of the code requirements, 51 single span specimens are gathered. In the associate literature, shear cracks were reported, originating from the web. The experimental found shear capacity is compared with the predicted mean resistance to web shear cracking based on the code requirements. For the specimens uncracked in bending the predictions appear to be accurate and the level of approximation approach suitable. For the specimens cracked in bending, on the other hand, the predictions appear to be conservative. This is caused by the conditions within which the formulas for shear tension are applicable. Not the shear tension formulas but the formulas for flexural shear are applicable for a considerable part of the specimens. This is the case despite the observation that shear cracks in the specimens originated from the web instead of from the flexural cracks in the flange. The application conditions within which the shear tension formulas are applicable appear to be the most relevant topic for future research and offers the best possibility to improve the accuracy of shear tension code requirements.

On the Potential of Lattice Type Model for Predicting Shear Capacity of Reinforced Concrete and SHCC Structures

Due to the brittle nature of shear failure, shear capacity is considered to be one of the most critical and relevant issues in the design of concrete structures. In this research, the possibility of using a discrete lattice model to predict the shear capacity of reinforced concrete beams is investigated. Beams without shear reinforcement and with different beam geometry and varying reinforcement ratios were studied and fracture behaviour from the simulations is compared to experimental results.

Acoustic emission measurement in the proof loading of an existing bridge affected by ASR

Proof loading has been considered as an effective approach in the assessment of existing concrete bridges. This paper presents a study of acoustic emission measurement in a proof loading of an ASR affected concrete slab bridge (Zijlweg bridge). Because of the uncertainty on the mechanical properties of the ASR affected concrete. The attenuation contours, the wave speed and the geometry effect were studied before the proof loading. During the proof loading, zonal location based on signal strength was applied to track the cracking active area. In addition, the combination of load ratio and calm ratio was used to assess the damage level caused by proof loading. The study showed that the additional damage caused by proof loading was limited. Besides, the presented approach appears to be a promising tool for proof loading.