Concrete Slab Bridges Research Articles

Determining load-carrying capacity and remaining lifetime of bridge in Vitanova, Slovakia

The paper is focused on diagnostic and calculation of load-carrying capacity of bridge object in village Vitanova in Slovakia. The bridge is on the road II/520 connecting town Tvrdošín and village Suchá Hora near border with Poland and bypass the Oravica River. The bridge object was built in 1957, so, it was 60 years old bridge in time of calculation (2017). It is reinforced concrete slab bridge of two single independent spans. In 2016, the Department of Structures and Bridges, the Faculty of Civil Engineering, University of Žilina, was asked to carry out the construction and technical survey and diagnostic of above mentioned bridge. The visual inspection, diagnostic, verifying real dimensions and material characteristics were requested. In 2017, the calculation of load-carrying capacity was done. For determining the load-carrying capacity, the standard approach given in Eurocodes was used. As an alternative, the modified (lower) reliability levels and their adequate partial safety factors according to Eurocodes were used. Moreover, the real traffic load was used for calculation of reliability index β and the failure probability Pf.

Deep Embedment (DE) FRP Shear Strengthening of Concrete Bridge Slabs under Loads Close to Supports

Shear forces are the most common governing failure mechanism of reinforced concrete bridge deck slabs subjected to loads close to their supports. This paper reveals a comprehensive study of the behaviour of concrete slabs shear-strengthened with a deep embedment fibre reinforced polymer (FRP) technique. In the experimental investigation, a series of eight full scale concrete slabs were created and tested up to failure. Several structural variables were changed to assess the effectiveness of this shear strengthening technique. The behaviour of test slabs is discussed and the influence of this strategy was evaluated by comparing the test results. It was shown that brittle shear failures could be avoided by using this strengthening strategy. The ultimate capacity and deflection at the failure were both enhanced by using the deep embedment strengthening method. Additionally, a nonlinear finite element analysis (NLFEA) was proposed to develop further investigation. This NLFEA model gave excellent predictions for the structural behaviour of the test concrete slabs. Finally, a two-way theoretical model was proposed to predict the loading-carrying capacity of concrete slabs strengthened with deep embedment FRP bars. The ultimate strength predicted by this theoretical method showed good agreement with that from the test results.

Embodied Energy Optimization of Prestressed Concrete Slab Bridge Decks

This paper presents one approach to the analysis and design of post-tensioned cast-in-place concrete slab bridge decks. A Simulated Annealing algorithm is applied to two objective functions: (i) the economic cost; and (ii) the embodied energy at different stages of production materials, transport, and construction. The problem involved 33 discrete design variables: five geometrical ones dealing with the thickness of the slab, the inner and exterior web width, and two flange thicknesses; concrete type; prestressing cables, and 26 variables for the reinforcement set-up. The comparison of the results obtained shows two different optimum families, which indicates that the traditional criteria of economic optimization leads to inefficient designs considering the embodied energy. The results indicate that the objectives are not competing functions, and that optimum energy designs are close to the optimum cost designs. The analysis also showed that the savings of each kW h of energy consumed carries an extra cost of 0.49€. The best cost solution presents 5.3% more embodied energy. The best energy solution is 9.7% more expensive than that of minor cost. In addition, the results have showed that the best cost solutions are not the best energy solutions.

Neural Network-Based Formula for Shear Capacity Prediction of One-Way Slabs Under Concentrated Loads

According to the current codes and guidelines, shear assessment of existing reinforced concrete slab bridges sometimes leads to the conclusion that the bridge under consideration has insufficient shear capacity. The calculated shear capacity, however, does not consider the transverse redistribution capacity of slabs, thus leading to overconservative values. This paper proposes an artificial neural network (ANN)-based formula to come up with estimates of the shear capacity of one-way reinforced concrete slabs under a concentrated load, based on 287 test results gathered from the literature. The proposed model yields maximum and mean relative errors of 0.0% for the 287 data points. Moreover, it was illustrated to clearly outperform (mean Vtest / VANN =1.00) the Eurocode 2 provisions (mean VE,EC / VR,C =1.59) for that dataset. A step-by-step assessment scheme for reinforced concrete slab bridges by means of the ANN-based model is also proposed, which results in an improvement of the current assessment procedures.

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

Development of recommendations for proof load testing of reinforced concrete slab bridges

As the bridge stock in the Netherlands and Europe is ageing, various methods to analyze existing bridges are being studied. Proof load testing of bridges is an option to experimentally demonstrate that a given bridge can carry the prescribed live loads. Based on extensive research on proof load testing of reinforced concrete slab bridges carried out in the Netherlands, recommendations for proof load testing of reinforced concrete slab bridges were developed. The recommendations for the preparation, execution, and post-processing of a proof load test are summarized in this paper. The novelty of the recommendations is that proof load testing for shear is studied, and that a proposal for stop criteria for shear and bending moment has been formulated. Further research on the shear behavior is necessary, after which the recommendations will be converted in guidelines for the industry.

Erratum

Structural ConcreteVolume 19, Issue 1 p. 325-325 ERRATUMFree Access Erratum This article corrects the following: Levels of approximation for the shear assessment of reinforced concrete slab bridges Eva Lantsoght, Ane Boer, Cor Veen, Volume 18Issue 1Structural Concrete pages: 143-152 First Published online: March 22, 2017 First published: 06 September 2017 https://doi.org/10.1002/suco.201770051AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat This paper1 was originally published with an incorrect caption for Figure 5. The caption should read as follows: FIGURE 5. Determination of distribution width for the peak of the shear stress in linear finite element models: (a) distribution of the forces measured in the experiment, showing the central load cell and load cells within 4d from center of the load for the ULS load level (1,314 kN); (b) shear stress distribution in linear finite element model, showing distance 4d from the center of the load, for the SLS load level (585 kN). REFERENCE 1Lantsoght E, de Boer A, van der Veen C. Levels of approximation for the shear assessment of reinforced concrete slab bridges. Struct Concr. 2017; 18: 143- 152. https://doi.org/10.1002/suco.201600012. Volume19, Issue1Special Issue: Special Issue on ShearFebruary 2018Pages 325-325 ReferencesRelatedInformation

16.26: Design and construction of composite bridges

ABSTRACTComposite bridges, where steel girders are used compositely with a concrete deck slab, can be preferred over steel or concrete bridges due several reasons. They are less expensive and require less maintenance than orthotropic steel decks and they are lighter than concrete girders. They often require less temporary structures for execution and by using prefabricated elements fast erection can be achieved. Composite bridges are often chosen for span ranges that are in between the typical span ranges of concrete and steel bridges.When designing a composite bridge deck it is important to carefully consider the different material characteristics of steel and concrete to achieve an optimum design both in respect of erection sequence and material quantities. The concrete slab has a high resistance to compression forces whereas steel is prone to buckling, but has a high tension capacity.The Constantine ramp bridges (Algeria, 2014) are open steel box girders with a filigran concrete slab. They are located on steep slopes in a congested urban area, which gave limitations to the construction methods. A composite deck solution was chosen so that steel segments could first be lifted into place by a medium size crane and secondly prefabricated concrete slab filigran members could be placed on the steel and used as formwork for the final in situ casting of the concrete slab. The construction sequence was planned so that the concrete slab would be mainly in compression in the dead load situation to optimize material quantities.Composite bridge decks are often applied in cable stayed bridges, since the concrete slab has good abilities to resist the high compression induced by the inclined cable stays particularly near the towers. Examples of recent composite cable stay bridges are Busan Bridges (Korea 2014, main span 475 m) and New NY Bridge (New York, under construction, main span 366 m) where bolted wide flange steel girders were used in combination with a concrete slab and Sungai Johor Bridge (Malaysia 2013, main span 500 m) where an open box section was applied.Composite bridge decks are often used in combination with all steel or all concrete decks to balance the weight when for example the main span is very large compared to the back spans such as for the Stonecutters bridge (Hong Kong, 2009, Main Span 1018m).

Load-Capacity Rating of Bridge Populations through Machine Learning: Application of Decision Trees and Random Forests

The functionality of the U.S. transportation infrastructure system is dependent upon the health of an aging network of over 600,000 bridges, and agencies responsible for maintaining these bridges rely on the process of load rating to assess the adequacy of individual structures. This paper presents a new approach for safety screening and load-capacity evaluation of large bridge populations that seeks to uncover heretofore unseen patterns within the National Bridge Inventory database and establish relationships between select bridge attributes and their load-capacity status. Decision-tree and random-forest classification models were trained on the national concrete slab bridge data set of over 40,000 structures. The resulting models were validated on an independent data set and then compared with a number of existing judgment-based schemes found in an extensive survey of the current state of practice in the United States. The proposed approach offers a method that provides guidance for improved allocation of resources by informing maintenance decisions through rapid identification of candidate bridges that require further scrutiny for either possible load restriction or restriction removal.

Distribution of peak shear stress in finite element models of reinforced concrete slabs

Existing reinforced concrete solid slab bridges in the Netherlands are re-assessed for shear based on a Unity Check: the ratio of the shear stress caused by the applied loads to the shear capacity of the concrete cross-section. The governing shear stress resulting from the self-weight, weight of the wearing surface, distributed and concentrated live loads, can be determined with a simplified spreadsheet-based method, the Quick Scan (Level of Assessment I) as well as with a linear finite element model (Level of Assessment II). When a finite element model is used, a distribution of shear stresses over the width of the slab bridge is automatically found. To compare the governing shear stress caused by the loads to the shear capacity, it is necessary to determine over which width the peak shear stress from the finite element model can be distributed. To answer this question, a finite element model is compared to an experiment. The experiment consists of a continuous, reinforced concrete slab subjected to a single concentrated load close to the support. Seven bearings equipped with load cells that measure the reaction force profile along the width of the slab are used to compare to the stress profile obtained from the finite element model. From this analysis, it is found that the peak shear stress in a linear finite element model can be distributed over 4dl with dl the effective depth to the longitudinal reinforcement of the slab. The comparison of measured reaction force profiles over the support to the stress profile from a finite element model results in a research-based distribution width that replaces the rules of thumb that were used until now.

Influence of railings on load carrying capacity of concrete slab bridges

Influence of railings on load carrying capacity of concrete slab bridges

Probabilistic lifetime performance and structural capacity analysis of continuous reinforced concrete slab bridges

A reliability-based method was developed for predicting the initiation time and the probability of flexural failure for continuous slab bridges with load-induced cracks exposed to chloride environment resulting from de-icing salts. A practical methodology was used for predicting the diffusion coefficient of chloride ingress into the pre-existing load-induced cracks in concrete. The reduction in the cross-sectional area of the reinforcement due to corrosion was included in the model. The proposed methodology accounts for uncertainties in the strength demand, structural capacity, and corrosion models, as well as uncertainties in environmental conditions, material properties, and structural geometry. All probabilistic data on uncertainties were estimated from the information contained in previous experimental and statistical studies. As an application of the proposed model, a three-span continuous slab bridge in Ohio is presented for demonstration of the developed methodology. A comparison of results clearly shows the importance of considering the effects of the load-induced cracks for correct prediction of the initiation of corrosion time and the critical time to maintain structural integrity.

Extended Strip Model for slabs subjected to load combinations

The loads that are used for the assessment of existing reinforced concrete slab bridges are the self-weight, superimposed loads, and distributed and concentrated live loads. As such, the shear capacity of reinforced concrete slabs under a combination of distributed and concentrated live loads is a topic of practical relevance. For slabs subjected to a single concentrated load, a plastic model for assessment exists: the Extended Strip Model, developed based on the Strip Model for concentric punching shear. A further adaptation of the model to assess slabs subjected to distributed and concentrated loads is presented in this paper. The proposed model is compared to experiments on slabs subjected to a single concentrated load and a line load. The conclusion of this comparison is that the Extended Strip Model results in a safe estimate of the maximum concentrated load on the slab, and that the method can be used for the assessment of existing bridges subjected to heavy truck loads.

Proof load testing of reinforced concrete slab bridges in the Netherlands

The bridges built during the development of the Dutch road network after the Second World War are reaching their originally devised service life. A large subset of the Dutch bridge stock consists of reinforced concrete slab bridges. This bridge type often rates insufficient according to the recently introduced Eurocodes. Therefore, more suitable methods are developed to assess reinforced concrete slab bridges to help transportation officials make informed decisions about the safety and remaining life of the existing bridges. Field testing can be used for example when the effect of deterioration on the structural capacity is unknown. A proof load test demonstrates that a given bridge can carry a certain load level. In the Netherlands, a number of existing reinforced concrete slab bridges have been proof loaded, and one bridge has been tested to collapse. Bridges with and without material damage were tested. These bridges were heavily instrumented, in order to closely monitor the behavior of the bridge. Critical positions for bending moment and shear were studied. Based on the proof load tests that were carried out over the past years, a set of recommendations for the systematic preparation, execution, and analysis of proof load test results is compiled. These recommendations will ultimately form the basis of the guideline for proof load testing for the Netherlands, which is currently under development.

Levels of approximation for the shear assessment of reinforced concrete slab bridges

Many existing reinforced concrete bridges in The Netherlands are suspected of having insufficient shear strength, hence a methodical approach is necessary to assess them. The aim of this paper is to provide a structured approach for assessment of the reinforced concrete slab bridges, which make up a considerable proportion of the Dutch bridge stock. The proposed method uses the levels of approximation introduced in the fib Model Code for Concrete Structures 2010. The recommendations at all levels are linked to experimental research. The different levels include spreadsheet-based calculations (the “Quick Scan”), linear finite element models, nonlinear finite element models, the analysis of a structure with cracked concrete, and, for exceptional cases, proof loading of the structure. The result of this approach is a structured method of levels of assessment that can be used when many bridges need to be assessed. For most bridges, assessment at the lowest level will prove sufficient. For a limited number of cases, higher levels of assessment will offer options and guidelines for a more in-depth study of the structure being assessed.

Performance Evaluation of a Reinforced Concrete Slab Bridge Retrofitted with Carbon Fiber Reinforcement Polymer Laminate System

As a result of a drawing oversight, a nine-span continuous reinforced concrete slab bridge on westbound I-10 near Lordsburg, New Mexico, was built with only half of the required positive moment steel reinforcement. Bridge 9367, constructed in April 2006, was retrofitted with a carbon fiber–reinforced polymer (CFRP) laminate system in November 2006 to correct for this error. Diagnostic load tests were conducted before and immediately after the retrofitting of the bridge. A finite element analysis of the bridge was also conducted to evaluate the strength and serviceability of the slab bridge and to determine whether the addition of the CFRP system effectively met these limit states. The addition of the CFRP to the bridge increased the rating factors to greater than the legal load limit. Before the bridge retrofit, stresses in the steel reinforcement exceeded the limits set to control excessive concrete cracking and inelastic deformations. Inclusion of the CFRP reduced these stresses but only slightly below the limits. Creep rupture and fatigue of the CFRP were not considered issues. Two additional load tests were conducted 8 months and approximately 9 years after the retrofit. The first evaluation showed that in the short term, the slab stiffness was increased with a decrease in measured strains immediately after the installation of the CFRP. However, comparison of the strains from the load tests conducted later showed that the magnitudes had greatly increased and were approximately equal to the preretrofit strains. Ultimately, Bridge 9367 was replaced due to excessive cracking and large measured strains.

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

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.

Ruytenschildt Bridge: Field and laboratory testing

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. Previous testing was limited to half-scale slab specimens cast in the laboratory. To study the full structural behavior of slab bridges, testing to failure of a bridge is necessary. In August 2014, a bridge was tested to failure in two spans. Afterwards, beams were sawn out of the bridge for experimental work in the laboratory and further study. Though calculations with current design provisions showed that the bridge could fail in shear, the field test showed failure in flexure before shear. The experiments on the beams study the transition from flexural to shear failure and the influence of the type of reinforcement on the capacity. The experimental results were compared to predictions of the capacity for the bridge slab and the sawn beams. These comparisons show that the current methods for rating of existing reinforced concrete slab bridges, leading to a sharper assessment, are conservative. It was also found that the application of plain bars instead of deformed bars does not increase the shear capacity of beams.

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.

Indirect fatigue evaluation of CFRP-reinforced bridge deck slabs under variable amplitude cyclic loading

Currently, bridge deck slabs reinforced with Fiber Reinforced Polymer (FRP) bars have been widely studied and applied to the bridge deck slabs in North America. However, there is still a lack of knowledge on the structural performance of the concrete bridge slabs reinforced using FRP bars, especially Carbon Fiber Reinforced Polymer (CFRP) bars. This aim of this study was to investigate the fatigue performance of bridge deck slabs reinforced with CFRP bars. The fatigue capacity was investigated using indirect fatigue evaluation when the number of cycles to failure was unknown, by using the equivalent number of cycles. The variable amplitude cyclic loadings effectively contribute to damage acceleration even at fatigue cycles of 1,000,000. The evaluation of fatigue capacity with respect to serviceability showed that deflection and crack width under variable amplitude loading were evaluated over a reasonable range to ensure that serviceable capacity is satisfied for CFRP bar reinforced bridge slabs. For fatigue design, S-N curves were analyzed using the different fatigue life models proposed by previous studies. It was found that the fatigue limit under variable amplitude loading should be analyzed by using the fatigue life model based on the variable amplitude loading cases.