YY
Y. Yang
info
Please Note
<p>This page displays the records of the person named above and is not linked to a unique person identifier. This record may need to be merged to a profile.</p>
92 records found
1
Journal article
(2026)
-
Gabriela Zarate Garnica, Fengqiao Zhang, Yuguang Yang, Max A.H. Hendriks, Eva O.L. Lantsoght
Proof load testing on bridges requires high magnitude loads. Stop criteria are used to avoid irreversible damage or failure during proof load testing. These stop criteria are thresholds to measurable parameters during the test. After reaching a stop criterion, the proof load test needs to be terminated. While in the past, stop criteria have been identified as a single level, this research proposes to use a traffic light system for stop criteria: green light (related to the serviceability limit state), yellow light (as an intermediate level) and red light (further testing is not permitted). The green light relates to the development of cracking, whereas the yellow and red light relate to the failure modes of flexure and shear. To develop stop criteria for the brittle failure mode of shear, thresholds are derived from mechanical models, based on strain measurements and crack widths, as well as using acoustic emission measurements. To validate the stop criteria, three series of experiments are analyzed: reinforced concrete slab strips, straight slabs, and skewed slabs. While field validation of the traffic light system is pending, the developed tool is a step forward to safely test concrete bridges without shear reinforcement.
...
Proof load testing on bridges requires high magnitude loads. Stop criteria are used to avoid irreversible damage or failure during proof load testing. These stop criteria are thresholds to measurable parameters during the test. After reaching a stop criterion, the proof load test needs to be terminated. While in the past, stop criteria have been identified as a single level, this research proposes to use a traffic light system for stop criteria: green light (related to the serviceability limit state), yellow light (as an intermediate level) and red light (further testing is not permitted). The green light relates to the development of cracking, whereas the yellow and red light relate to the failure modes of flexure and shear. To develop stop criteria for the brittle failure mode of shear, thresholds are derived from mechanical models, based on strain measurements and crack widths, as well as using acoustic emission measurements. To validate the stop criteria, three series of experiments are analyzed: reinforced concrete slab strips, straight slabs, and skewed slabs. While field validation of the traffic light system is pending, the developed tool is a step forward to safely test concrete bridges without shear reinforcement.
Impact of creep and shrinkage models in predicting deflection and prestress losses of balanced cantilever box girder bridges
A case study with multi-decade deflection measurements
Journal article
(2026)
-
Emilia Andrade Borges, Arthur Slobbe, Gijs Eumelen, Bart van den Broek, Jasper Doorgeest, Yuguang Yang
Current code-based models for concrete creep and shrinkage present significant challenges when applied to large structures such as balanced cantilever box girder bridges, due to their complex geometry and staged construction. Case studies on such structures with multi-decade deflection measurements, though scarce in literature, are essential for evaluating the long-term accuracy of these models. This paper presents a unique case study of a three-span balanced cantilever box girder bridge in the Netherlands with 44 years of deflection measurements, revealing excessive and ongoing deflections. A detailed finite element model incorporating construction stages was developed to study the impact of four creep and shrinkage models on the predictions of multi-decade deflections and prestress losses. All models significantly underestimated long-term deflections, by about 75% for Eurocode 2 (2004), Eurocode 2 (2023), and fib Model Code 2010, and 35% for RILEM B4. The choice of the creep and shrinkage model also strongly affects the predicted prestress losses, with RILEM B4 estimating losses up to 1.7 times higher than Eurocode 2 (2004). Since the working prestress level is a key factor for structural assessment of large-span concrete bridges, these findings have important implications for engineering practice. Supported by rare long-term validation data, this study reveals the performance and limitations of current creep and shrinkage models, the possible consequences of their underestimations, and the need for more reliable long-term prediction models for the design and assessment of box girder bridges.
...
Current code-based models for concrete creep and shrinkage present significant challenges when applied to large structures such as balanced cantilever box girder bridges, due to their complex geometry and staged construction. Case studies on such structures with multi-decade deflection measurements, though scarce in literature, are essential for evaluating the long-term accuracy of these models. This paper presents a unique case study of a three-span balanced cantilever box girder bridge in the Netherlands with 44 years of deflection measurements, revealing excessive and ongoing deflections. A detailed finite element model incorporating construction stages was developed to study the impact of four creep and shrinkage models on the predictions of multi-decade deflections and prestress losses. All models significantly underestimated long-term deflections, by about 75% for Eurocode 2 (2004), Eurocode 2 (2023), and fib Model Code 2010, and 35% for RILEM B4. The choice of the creep and shrinkage model also strongly affects the predicted prestress losses, with RILEM B4 estimating losses up to 1.7 times higher than Eurocode 2 (2004). Since the working prestress level is a key factor for structural assessment of large-span concrete bridges, these findings have important implications for engineering practice. Supported by rare long-term validation data, this study reveals the performance and limitations of current creep and shrinkage models, the possible consequences of their underestimations, and the need for more reliable long-term prediction models for the design and assessment of box girder bridges.
This work presents a concrete-specific analytical framework for modelling body-wave scattering by explicitly tailoring multiple-scattering theory to the microstructural characteristics of concrete. Instead of treating scattering parameters as abstract statistical quantities, the framework parameterizes the key inputs of scattering theory in terms of physically measurable concrete attributes, including coarse aggregate size, volume fraction, and the material property contrast between the matrix and the dominant scattering phase, whether coarse aggregates or the interfacial transition zone. By embedding these microstructure-informed parameters into a two-phase spatial statistical formulation, closed-form expressions for total and transport scattering cross-sections are derived and directly linked to ultrasonic diffusivity through diffuse wave theory. Experimental validation using geopolymer concrete members and published data for ordinary concrete demonstrates consistent agreement between theoretical predictions and experimental measurements across a broad frequency range. The proposed framework therefore renders body-wave scattering in concrete quantitatively computable from material composition, providing a physically grounded basis for quantitative interpretation of diffuse wave transport, energy equilibration, and coda-wave velocity changes without reliance on ad hoc fitting parameters.
...
This work presents a concrete-specific analytical framework for modelling body-wave scattering by explicitly tailoring multiple-scattering theory to the microstructural characteristics of concrete. Instead of treating scattering parameters as abstract statistical quantities, the framework parameterizes the key inputs of scattering theory in terms of physically measurable concrete attributes, including coarse aggregate size, volume fraction, and the material property contrast between the matrix and the dominant scattering phase, whether coarse aggregates or the interfacial transition zone. By embedding these microstructure-informed parameters into a two-phase spatial statistical formulation, closed-form expressions for total and transport scattering cross-sections are derived and directly linked to ultrasonic diffusivity through diffuse wave theory. Experimental validation using geopolymer concrete members and published data for ordinary concrete demonstrates consistent agreement between theoretical predictions and experimental measurements across a broad frequency range. The proposed framework therefore renders body-wave scattering in concrete quantitatively computable from material composition, providing a physically grounded basis for quantitative interpretation of diffuse wave transport, energy equilibration, and coda-wave velocity changes without reliance on ad hoc fitting parameters.
Alkali-activated concrete (AAC) is a sustainable alternative to ordinary Portland cement concrete, but its large-scale structural performance remains insufficiently understood, particularly in terms of long-term durability. To ensure safe application, continuous monitoring of AAC structures is essential. This paper develops and validates ultrasonic-based damage indicators (DIs) intended to support future lifetime monitoring of precast AAC bridge members. Full-scale laboratory tests were performed on two prestressed AAC beams and a solid slab consisting of three beams with embedded piezoelectric sensors. Active ultrasonic measurements collected throughout loading were processed to derive two DIs: (1) reduction in waveform coherency using direct wave interferometry to indicate crack initiation, and (2) relative wave velocity obtained from an arrival-time picker to track crack propagation. The waveform coherency-based DI consistently identified the onset of cracking at or even before the first visible cracks appeared in digital image correlation (DIC) images, while the velocity-based DI provided a qualitative measure of crack propagation and orientation. Both indicators responded sensitively once degradation developed, enabling early warning of structural deterioration. The validated DIs are intended to inform the development of a lifetime monitoring scheme on a pilot precast AAC bridge on a Dutch national road. This study also provides a practical pathway toward risk-informed operation and broader adoption of AAC in bridge applications.
...
Alkali-activated concrete (AAC) is a sustainable alternative to ordinary Portland cement concrete, but its large-scale structural performance remains insufficiently understood, particularly in terms of long-term durability. To ensure safe application, continuous monitoring of AAC structures is essential. This paper develops and validates ultrasonic-based damage indicators (DIs) intended to support future lifetime monitoring of precast AAC bridge members. Full-scale laboratory tests were performed on two prestressed AAC beams and a solid slab consisting of three beams with embedded piezoelectric sensors. Active ultrasonic measurements collected throughout loading were processed to derive two DIs: (1) reduction in waveform coherency using direct wave interferometry to indicate crack initiation, and (2) relative wave velocity obtained from an arrival-time picker to track crack propagation. The waveform coherency-based DI consistently identified the onset of cracking at or even before the first visible cracks appeared in digital image correlation (DIC) images, while the velocity-based DI provided a qualitative measure of crack propagation and orientation. Both indicators responded sensitively once degradation developed, enabling early warning of structural deterioration. The validated DIs are intended to inform the development of a lifetime monitoring scheme on a pilot precast AAC bridge on a Dutch national road. This study also provides a practical pathway toward risk-informed operation and broader adoption of AAC in bridge applications.
No practically viable method yet exists to provide minimum shear reinforcements into pretensioned precast hollow-core slab (PHCS) units produced through an automated extrusion method. Subsequently, the web-shear strength of PHCS units with untapped depths greater than 315 mm (12.5 in.) should be reduced in half, according to current ACI 318 shear design provisions. Meanwhile, continuous precast floor construction has been commonly adopted in current practices by using cast-in-place (CIP) topping and/or core-filling concrete. However, shear test results on continuous composite PHCS members subjected to combined shear and negative bending moment are very limited in literature. To this end, this study conducts shear tests of thick composite PHCS members with untapped depths greater than 315 mm (12.5 in.) and various span-depth ratios subjected to negative bending moments, where noncomposite and composite PHCS units subjected to shear combined with positive bending were also tested for comparison purposes. Test results show that flexure-shear strength can dominate the failure mode of continuous PHCS members rather than the web-shear failure, depending on the presence of CIP topping concrete and shear span-depth ratio. In addition, it was also confirmed that the shear strength of composite PHCS members is marginally improved by using a core-filling method under negative bending moment at continuous support, and thus its shear contribution seems not fully code-compliant and satisfactory to that estimated using ACI 318 shear design equations.
...
No practically viable method yet exists to provide minimum shear reinforcements into pretensioned precast hollow-core slab (PHCS) units produced through an automated extrusion method. Subsequently, the web-shear strength of PHCS units with untapped depths greater than 315 mm (12.5 in.) should be reduced in half, according to current ACI 318 shear design provisions. Meanwhile, continuous precast floor construction has been commonly adopted in current practices by using cast-in-place (CIP) topping and/or core-filling concrete. However, shear test results on continuous composite PHCS members subjected to combined shear and negative bending moment are very limited in literature. To this end, this study conducts shear tests of thick composite PHCS members with untapped depths greater than 315 mm (12.5 in.) and various span-depth ratios subjected to negative bending moments, where noncomposite and composite PHCS units subjected to shear combined with positive bending were also tested for comparison purposes. Test results show that flexure-shear strength can dominate the failure mode of continuous PHCS members rather than the web-shear failure, depending on the presence of CIP topping concrete and shear span-depth ratio. In addition, it was also confirmed that the shear strength of composite PHCS members is marginally improved by using a core-filling method under negative bending moment at continuous support, and thus its shear contribution seems not fully code-compliant and satisfactory to that estimated using ACI 318 shear design equations.
Validation of proof loading methods
With a basis in collapse testing and stop criteria crack evaluation
Conference paper
(2025)
-
Jacob Wittrup Schmidt, Christian Overgaard Christensen, Kenneth Dahl Schiøttz Damsgaard, Eva O.L. Lantsoght, Yuguang Yang, Per Goltermann
Safe proof loading of concrete bridges requires reliable stop criteria. Such criteria must ensure sufficient margin to the ultimate resistance and may be based on observations from advanced testing. In particular, the identification of thresholds related to pre-stressed and non-shearreinforced slab structures is currently ongoing with an addition of specific focus on potentially brittle failure modes of such structures. This paper presents representative examples of identifying stop criteria and target load thresholds using a combination of laboratory- and in-situ testing. Responses from recently tested structures and structural elements will be presented to enable discussion and perspectivation. The presented test results show measurable warning with sufficient margin from crack initiation to stop criterion. It was additionally seen that the target load often may be the governing threshold when proof load testing.
...
Safe proof loading of concrete bridges requires reliable stop criteria. Such criteria must ensure sufficient margin to the ultimate resistance and may be based on observations from advanced testing. In particular, the identification of thresholds related to pre-stressed and non-shearreinforced slab structures is currently ongoing with an addition of specific focus on potentially brittle failure modes of such structures. This paper presents representative examples of identifying stop criteria and target load thresholds using a combination of laboratory- and in-situ testing. Responses from recently tested structures and structural elements will be presented to enable discussion and perspectivation. The presented test results show measurable warning with sufficient margin from crack initiation to stop criterion. It was additionally seen that the target load often may be the governing threshold when proof load testing.
The concrete slab bridge on Balladelaan in the Netherlands was built in 1946. It is a cast-in-place concrete bridge with five spans that together form a statically indeterminate deck system. For this type of concrete bridge, shear failure often appears to be the critical failure mechanism, raising concerns about the structural capacity and remaining service life of the bridge. Additionally, the bridge has undergone several undocumented modifications over its lifetime, making it difficult to accurately assess its safety. To monitor this bridge and predict its structural capacity, 22 ultrasonic sensors, known as Smart Aggregates (SAs), and 16 temperature sensors were embedded in the bridge by drilling holes to track changes such as crack development, stress variations, and temperature fluctuations. This paper presents the initial phase measurements from the SAs and temperature sensors in the monitoring project. The main goals of this phase are (1) to ensure that the installed sensors function properly and (2) to establish a preliminary correlation between the measurements from the SAs and the temperature sensors.
...
The concrete slab bridge on Balladelaan in the Netherlands was built in 1946. It is a cast-in-place concrete bridge with five spans that together form a statically indeterminate deck system. For this type of concrete bridge, shear failure often appears to be the critical failure mechanism, raising concerns about the structural capacity and remaining service life of the bridge. Additionally, the bridge has undergone several undocumented modifications over its lifetime, making it difficult to accurately assess its safety. To monitor this bridge and predict its structural capacity, 22 ultrasonic sensors, known as Smart Aggregates (SAs), and 16 temperature sensors were embedded in the bridge by drilling holes to track changes such as crack development, stress variations, and temperature fluctuations. This paper presents the initial phase measurements from the SAs and temperature sensors in the monitoring project. The main goals of this phase are (1) to ensure that the installed sensors function properly and (2) to establish a preliminary correlation between the measurements from the SAs and the temperature sensors.
Many existing concrete structures require effective assessment of the bearing capacity. A critical failure mode is shear, especially for concrete structures without or with limited shear reinforcement. The shear failure is brittle and often leads to loss of property and lives. Therefore the shear failure should be indicated before it occurs. A potential solution is to use acoustic emission (AE) monitoring, which is sensitive to minor changes in concrete, even micro-cracking, both on the surface and inside the structure. By combining the knowledge of shear failure processes and AE techniques, this paper presents an AE-based shear failure indication system. The system automatically identifies three levels of structural damage levels up to shear failure, which are categorized from minor to severe levels as green-light, yellow-light, and red-light criteria. The 'traffic light system' is validated using six shear tests on full-scale reinforced concrete beams without shear reinforcement. The robustness of the system is also validated across these tests.
...
Many existing concrete structures require effective assessment of the bearing capacity. A critical failure mode is shear, especially for concrete structures without or with limited shear reinforcement. The shear failure is brittle and often leads to loss of property and lives. Therefore the shear failure should be indicated before it occurs. A potential solution is to use acoustic emission (AE) monitoring, which is sensitive to minor changes in concrete, even micro-cracking, both on the surface and inside the structure. By combining the knowledge of shear failure processes and AE techniques, this paper presents an AE-based shear failure indication system. The system automatically identifies three levels of structural damage levels up to shear failure, which are categorized from minor to severe levels as green-light, yellow-light, and red-light criteria. The 'traffic light system' is validated using six shear tests on full-scale reinforced concrete beams without shear reinforcement. The robustness of the system is also validated across these tests.
Conference paper
(2025)
-
Jacob Wittrup Schmidt, Christian Overgaard Christensen, Kenneth Dahl Schiøttz Damsgaard, Eva O.L. Lantsoght, Yuguang Yang, Per Goltermann
The field of proof-loading has expanded over the last decade with excellent examples of successful collaborations and multidisciplinary approaches. Advanced testing has, as one of the essential subjects in an interdisciplinary assessment, brought significant value to further understanding of structural responses and failure mechanisms related to concrete bridges. This paper presents laboratory and field collapse testing examples in the Netherlands and Denmark, and related investigations of the response of non-shear reinforced slabs until failure. A special focus is dedicated to load application, examples of test approaches, some practical insights and test result comparison. Considerations of the laboratory and field test planning in synergy will be discussed based on the results and experiences obtained. A substantial margin to ultimate failure was found from crack identification or other measurable warnings in all tests. These observations suggests that it is possible to get sufficient warning even for non-shear reinforced concrete slabs structures.
...
The field of proof-loading has expanded over the last decade with excellent examples of successful collaborations and multidisciplinary approaches. Advanced testing has, as one of the essential subjects in an interdisciplinary assessment, brought significant value to further understanding of structural responses and failure mechanisms related to concrete bridges. This paper presents laboratory and field collapse testing examples in the Netherlands and Denmark, and related investigations of the response of non-shear reinforced slabs until failure. A special focus is dedicated to load application, examples of test approaches, some practical insights and test result comparison. Considerations of the laboratory and field test planning in synergy will be discussed based on the results and experiences obtained. A substantial margin to ultimate failure was found from crack identification or other measurable warnings in all tests. These observations suggests that it is possible to get sufficient warning even for non-shear reinforced concrete slabs structures.
Half-joints in concrete bridges are known to exhibit an increased rate of degradation. Their main vulnerability is situated in the re-entrant corner, buried deep inside the joint. This makes visual inspection nearly impossible. A Structural Health Monitoring (SHM) system offers a promising alternative, but interpretation of the half-joint status from SHM data is not straightforward. The study presented in this paper is a case study of the SHM system on the Naardertrekvaart bridge in the Netherlands. Analysis of SHM data revealed a dependence of the movement of the bridge on a seasonal temperature cycle, presumably caused by hindered thermal contraction of the half-joints. This phenomenon offered no reliable estimation of the half-joint status. In addition, from the movement of the lower half-joint nibs under traffic loads, a stiffness parameter was devised, used as an estimation of the half-joint status. The study indicated that a high-frequency approach can increase effectiveness of the SHM system.
...
Half-joints in concrete bridges are known to exhibit an increased rate of degradation. Their main vulnerability is situated in the re-entrant corner, buried deep inside the joint. This makes visual inspection nearly impossible. A Structural Health Monitoring (SHM) system offers a promising alternative, but interpretation of the half-joint status from SHM data is not straightforward. The study presented in this paper is a case study of the SHM system on the Naardertrekvaart bridge in the Netherlands. Analysis of SHM data revealed a dependence of the movement of the bridge on a seasonal temperature cycle, presumably caused by hindered thermal contraction of the half-joints. This phenomenon offered no reliable estimation of the half-joint status. In addition, from the movement of the lower half-joint nibs under traffic loads, a stiffness parameter was devised, used as an estimation of the half-joint status. The study indicated that a high-frequency approach can increase effectiveness of the SHM system.
Inverted T precast girders with a cast-in-situ topping layer, recognized as precast composite girders, are commonly used in Dutch bridge construction. Notably, the bridges built before 1974 often lacked sufficient shear reinforcement, raising concerns about their shear capacity under increasing traffic loads. However, how to assess these composite girders under the scope of the second-generation Eurocode remains challenging, as the shear formulations were originally developed for monolithic structural members. Consequently, their direct applicability to precast composite systems, due to the distinctive stress distribution in the web of the composite structural members, lacks theoretical substantiation and experimental validation. This study first presents the three alternative failure criteria equations based on the same theory, and after that, an experimental investigation of the shear behaviour of precast composite girders through two full-scale tests is discussed. The test data is later used to compare the alternative failure criteria.
...
Inverted T precast girders with a cast-in-situ topping layer, recognized as precast composite girders, are commonly used in Dutch bridge construction. Notably, the bridges built before 1974 often lacked sufficient shear reinforcement, raising concerns about their shear capacity under increasing traffic loads. However, how to assess these composite girders under the scope of the second-generation Eurocode remains challenging, as the shear formulations were originally developed for monolithic structural members. Consequently, their direct applicability to precast composite systems, due to the distinctive stress distribution in the web of the composite structural members, lacks theoretical substantiation and experimental validation. This study first presents the three alternative failure criteria equations based on the same theory, and after that, an experimental investigation of the shear behaviour of precast composite girders through two full-scale tests is discussed. The test data is later used to compare the alternative failure criteria.
Conference paper
(2025)
-
Gabriela Zarate Garnica, Fengqiao Zhang, Yuguang Yang, Max Hendriks, Eva Lantsoght
During a proof load test on a bridge, high magnitude loads are applied. To avoid causing irreversible damage, thresholds to the structural responses, the so-called stop criteria, need to be defined. This paper proposes to categorize stop criteria into three levels: green light (related to the serviceability limit state), yellow light (related to potential irreversible damage) and red light (related to potential local collapse). For the Ultimate Limit State, stop criteria for shear and flexure are defined. Shear stop criteria are derived from mechanical models, using traditional strain measurements and acoustic emission measurements. These stop criteria are validated with experiments on reinforced concrete slab strips, straight slabs, and skewed slabs. The resulting traffic light system gives the bridge engineer a tool to make decisions during a proof load test. This approach is a step forward in the interpretation of structural responses during proof load testing.
...
During a proof load test on a bridge, high magnitude loads are applied. To avoid causing irreversible damage, thresholds to the structural responses, the so-called stop criteria, need to be defined. This paper proposes to categorize stop criteria into three levels: green light (related to the serviceability limit state), yellow light (related to potential irreversible damage) and red light (related to potential local collapse). For the Ultimate Limit State, stop criteria for shear and flexure are defined. Shear stop criteria are derived from mechanical models, using traditional strain measurements and acoustic emission measurements. These stop criteria are validated with experiments on reinforced concrete slab strips, straight slabs, and skewed slabs. The resulting traffic light system gives the bridge engineer a tool to make decisions during a proof load test. This approach is a step forward in the interpretation of structural responses during proof load testing.
Journal article
(2025)
-
Yubao Zhou, Beyazit Bestami Aydin, Fengqiao Zhang, Max A.N. Hendriks, Yuguang Yang
The next generation of acoustic emission (AE) applications in concrete structural health monitoring (SHM) relies upon a reliable and quantitative relationship between AE measurements and corresponding AE sources. To achieve this, it is a prerequisite to accurately model the whole AE process that is a multiscale coupling process between local material fracturing and induced elastic wave propagation at structural level. Such a complex process, however, cannot be well addressed in currently available modelling methods. To fill this research gap, this study proposes a lattice modelling approach that achieves for the first time the explicit simulation of complete waveforms of transient AE signals induced by concrete fracture. The proposed approach incorporates an explicit time integration technique with a novel proportional-integral-derivative (PID) control algorithm for reducing spurious oscillations and a Rayleigh damping-based calculation and calibration method for the attenuation of AE waves. In this paper, the proposed lattice modelling approach is implemented to simulate the concrete Mode-I fracturing process in a three-point bending test. Besides the mechanical behaviors and AE hit number, a comparison was conducted between numerically and experimentally obtained AE waveforms. The AE waveforms and their attenuation characteristics simulated by the proposed lattice modelling method turn out to be comparable to experimental results. The proposed approach is of significance for a deep understanding of AE-related fracture mechanisms and a more reliable application of AE technique.
...
The next generation of acoustic emission (AE) applications in concrete structural health monitoring (SHM) relies upon a reliable and quantitative relationship between AE measurements and corresponding AE sources. To achieve this, it is a prerequisite to accurately model the whole AE process that is a multiscale coupling process between local material fracturing and induced elastic wave propagation at structural level. Such a complex process, however, cannot be well addressed in currently available modelling methods. To fill this research gap, this study proposes a lattice modelling approach that achieves for the first time the explicit simulation of complete waveforms of transient AE signals induced by concrete fracture. The proposed approach incorporates an explicit time integration technique with a novel proportional-integral-derivative (PID) control algorithm for reducing spurious oscillations and a Rayleigh damping-based calculation and calibration method for the attenuation of AE waves. In this paper, the proposed lattice modelling approach is implemented to simulate the concrete Mode-I fracturing process in a three-point bending test. Besides the mechanical behaviors and AE hit number, a comparison was conducted between numerically and experimentally obtained AE waveforms. The AE waveforms and their attenuation characteristics simulated by the proposed lattice modelling method turn out to be comparable to experimental results. The proposed approach is of significance for a deep understanding of AE-related fracture mechanisms and a more reliable application of AE technique.
Reinforced concrete solid slab bridges are often skewed to cross underlying objects, which increases the shear stress concentration at the obtuse corner. Limited experimental evidence on skewed slabs is available, so that both the shear capacity and failure mode in skewed slab bridges are subject to discussion. Therefore, an experimental program at Delft University of Technology investigated the capacity and failure modes in skewed slabs under concentrated loads near the edge. Results from 15 tests on five 1:2-scale slab members result in shear failures and show a decreasing capacity with increasing skew angles. The obtuse corner is found to be critical; the reinforcement layout did not influence the capacity significantly. Comparisons with calculation methods showed reasonable accuracy. A proposed method using a larger integration length around the peak shear stress obtained from linear finite element modeling may be recommended for assessment.
...
Reinforced concrete solid slab bridges are often skewed to cross underlying objects, which increases the shear stress concentration at the obtuse corner. Limited experimental evidence on skewed slabs is available, so that both the shear capacity and failure mode in skewed slab bridges are subject to discussion. Therefore, an experimental program at Delft University of Technology investigated the capacity and failure modes in skewed slabs under concentrated loads near the edge. Results from 15 tests on five 1:2-scale slab members result in shear failures and show a decreasing capacity with increasing skew angles. The obtuse corner is found to be critical; the reinforcement layout did not influence the capacity significantly. Comparisons with calculation methods showed reasonable accuracy. A proposed method using a larger integration length around the peak shear stress obtained from linear finite element modeling may be recommended for assessment.
Aggregate interlock is considered one of the most important shear transfer mechanisms in concrete members. In the well-established Two-Phase model proposed by Walraven in the 1980s, the shear stress transferred by aggregate interlock is estimated by calculating the projected contact areas of two crack surfaces. As one of the main assumptions in the model, the crack surface is idealized by a plain surface crossing randomly distributed, idealized spherical aggregates. This was a necessary simplification of an actual crack surface in the 1980s because of the lack of measurement equipment as well as computational capacity. With the development of high-accuracy 3D scanning techniques, new possibilities for modelling aggregate interlock have become available. This paper proposes a generalised method to determine the aggregate interlock stresses using the crack surface directly from 3D scanning. The proposed method is cross-verified with the Two-Phase model using the same simplified crack surface. A case study using the scanned crack surfaces of concrete cubes is conducted to investigate the influence of surface roughness. The proposed method provides a new possibility for conducting a refined investigation of the aggregate interlock for new concrete types, especially under the scope of the next-generation Eurocode shear provision.
...
Aggregate interlock is considered one of the most important shear transfer mechanisms in concrete members. In the well-established Two-Phase model proposed by Walraven in the 1980s, the shear stress transferred by aggregate interlock is estimated by calculating the projected contact areas of two crack surfaces. As one of the main assumptions in the model, the crack surface is idealized by a plain surface crossing randomly distributed, idealized spherical aggregates. This was a necessary simplification of an actual crack surface in the 1980s because of the lack of measurement equipment as well as computational capacity. With the development of high-accuracy 3D scanning techniques, new possibilities for modelling aggregate interlock have become available. This paper proposes a generalised method to determine the aggregate interlock stresses using the crack surface directly from 3D scanning. The proposed method is cross-verified with the Two-Phase model using the same simplified crack surface. A case study using the scanned crack surfaces of concrete cubes is conducted to investigate the influence of surface roughness. The proposed method provides a new possibility for conducting a refined investigation of the aggregate interlock for new concrete types, especially under the scope of the next-generation Eurocode shear provision.
The authors regret that the Fig. 6a of the article was incorrect. [...]
...
The authors regret that the Fig. 6a of the article was incorrect. [...]
Precast girders are mainly used as a simply supported system to build multi-span bridges. Alternatively, the precast girders can be made continuous at the intermediate support using cast in situ topping and cross beams. In the Netherlands, a substantial number of these bridges were designed and constructed in this way by following the design regulations in the past. When they are reassessed using Eurocode and the Guidelines for Assessment of Existing Bridges (RBK) by the Rijkswaterstaat (Dutch Ministry of Infrastructure and Water Management), their shear capacity turns out to be insufficient. Since almost no experimental data are available in the literature that can justify the code prediction for this bridge type, a dedicated experimental program has been established to investigate the actual shear behaviour. As a part of this program, this study presents the experimental observation of two full-scale 15 m long shear tests that were part of the recent blind contest at the Delft University of Technology. Using the experimental observations, the predictions of RBK, Model Code, and FprEN 1992-1-1:2023 (Draft for the 2nd generation of Eurocode 2 ) are examined. The comparison of the codes against the test shows safe and over-conservative predictions for both empirical and strain-based approaches.
...
Precast girders are mainly used as a simply supported system to build multi-span bridges. Alternatively, the precast girders can be made continuous at the intermediate support using cast in situ topping and cross beams. In the Netherlands, a substantial number of these bridges were designed and constructed in this way by following the design regulations in the past. When they are reassessed using Eurocode and the Guidelines for Assessment of Existing Bridges (RBK) by the Rijkswaterstaat (Dutch Ministry of Infrastructure and Water Management), their shear capacity turns out to be insufficient. Since almost no experimental data are available in the literature that can justify the code prediction for this bridge type, a dedicated experimental program has been established to investigate the actual shear behaviour. As a part of this program, this study presents the experimental observation of two full-scale 15 m long shear tests that were part of the recent blind contest at the Delft University of Technology. Using the experimental observations, the predictions of RBK, Model Code, and FprEN 1992-1-1:2023 (Draft for the 2nd generation of Eurocode 2 ) are examined. The comparison of the codes against the test shows safe and over-conservative predictions for both empirical and strain-based approaches.
The shear provision for members without shear reinforcement in the second generation of Eurocode has been changed to a new set of formulas based on the critical shear crack theory (CSCT). The formula is based on a shear failure criterion originally developed for reinforced concrete members without shear reinforcement. To allow its application as a design code type for formula, the original CSCT failure criterion undergoes several modifications, such that it can be used to verify the shear resistance of prestressed members as well. Since the new Eurocode shear provision will be applied to design and assess prestressed concrete members in Europe and many other countries in the world, it is important to extensively validate this model. This paper presents a validation study of three different variations of the CSCT strain-based failure criteria, including the one eventually employed in the second generation Eurocode shear provision, using the ACI-DAfStb shear database. The results are also compared with the current Eurocode shear provisions. The second generation Eurocode shear formula appears to be able to determine the shear resistance more accurately than the current one, even for prestressed concrete members without shear reinforcement while it was not actually developed for this. However, Annex I.8 shear formula may lead to an overestimation of the shear resistance for higher values of the effective span to depth ratio (acs/d).
...
The shear provision for members without shear reinforcement in the second generation of Eurocode has been changed to a new set of formulas based on the critical shear crack theory (CSCT). The formula is based on a shear failure criterion originally developed for reinforced concrete members without shear reinforcement. To allow its application as a design code type for formula, the original CSCT failure criterion undergoes several modifications, such that it can be used to verify the shear resistance of prestressed members as well. Since the new Eurocode shear provision will be applied to design and assess prestressed concrete members in Europe and many other countries in the world, it is important to extensively validate this model. This paper presents a validation study of three different variations of the CSCT strain-based failure criteria, including the one eventually employed in the second generation Eurocode shear provision, using the ACI-DAfStb shear database. The results are also compared with the current Eurocode shear provisions. The second generation Eurocode shear formula appears to be able to determine the shear resistance more accurately than the current one, even for prestressed concrete members without shear reinforcement while it was not actually developed for this. However, Annex I.8 shear formula may lead to an overestimation of the shear resistance for higher values of the effective span to depth ratio (acs/d).
Concrete-to-concrete interface behaviour in precast girder bridges made continuous
Deficiencies and challenges
Conference paper
(2024)
-
Emilia A. Andrade Borges, Yuguang Yang, Marco A. Roosen, Max A.N. Hendriks
Aging infrastructure in the Netherlands presents a significant challenge, particularly with precast girder bridges made continuous, which exhibit inadequate shear reinforcement per current design codes. To address shear capacity and accuracy of current assessment practices, a research program including full-scale shear tests is underway at Delft University of Technology. As a part of the research, a blind pre-diction contest with two specimens has been organized. The experiments showed that the loss of composite action at the interface is the primary failure mechanism, and generally an accurate model of the interface behaviour in such composite members is missing. In this paper, a further review of the available interface models and previous tests is conducted. This review leads to the challenges in the accurate evaluation of the interface behaviour, as well as the next steps to address them: a new set of full-scale specimens, and a small-scale test setup reflecting a realistic stress distribution.
...
Aging infrastructure in the Netherlands presents a significant challenge, particularly with precast girder bridges made continuous, which exhibit inadequate shear reinforcement per current design codes. To address shear capacity and accuracy of current assessment practices, a research program including full-scale shear tests is underway at Delft University of Technology. As a part of the research, a blind pre-diction contest with two specimens has been organized. The experiments showed that the loss of composite action at the interface is the primary failure mechanism, and generally an accurate model of the interface behaviour in such composite members is missing. In this paper, a further review of the available interface models and previous tests is conducted. This review leads to the challenges in the accurate evaluation of the interface behaviour, as well as the next steps to address them: a new set of full-scale specimens, and a small-scale test setup reflecting a realistic stress distribution.
As the existing bridge stock is ageing in various parts of the world, the topic of how to assess, maintain and/or improve, and manage existing bridges becomes increasingly important. Existing bridges may be designed according to outdated codes with requirements that may be considered unsafe nowadays, and for loads that are significantly different than those used nowadays. For those bridges, an accurate assessment leads to more efficient management of the bridge stock. This paper outlines various strategies that lead to an improvement of the assessment, and potentially to the extension of the service life of existing concrete bridges. This paper provides a selected examples that engineers who are faced with the assessment of ageing bridge can use. Ultimately, the presented insights can serve to support countries with a younger bridge stock in the development of an assessment strategy.
...
As the existing bridge stock is ageing in various parts of the world, the topic of how to assess, maintain and/or improve, and manage existing bridges becomes increasingly important. Existing bridges may be designed according to outdated codes with requirements that may be considered unsafe nowadays, and for loads that are significantly different than those used nowadays. For those bridges, an accurate assessment leads to more efficient management of the bridge stock. This paper outlines various strategies that lead to an improvement of the assessment, and potentially to the extension of the service life of existing concrete bridges. This paper provides a selected examples that engineers who are faced with the assessment of ageing bridge can use. Ultimately, the presented insights can serve to support countries with a younger bridge stock in the development of an assessment strategy.