Bridge deck slabs are members on which one-way reinforced concrete slabs are found frequently loaded by concentrated loads. Although the one-way shear failure mechanism has gathered more attention in the past years, both one-way shear and two-way shear mechanisms may be critical for such loading conditions. This paper addressed the ultimate capacity of thin one-way reinforced concrete slabs subjected to concentrated loads and yielding of the flexural reinforcement. In practice, the test setup studied was devised to represent short-span rural bridges frequently found in Brazil. The experimental program included 12 tests performed on 6 slabs applying the concentrated loads at varied positions. All tests started to fail by punching shear. Nevertheless, both one-way shear and punching shear cracks were observed at ultimate states after shear redistribution. The reinforcement yielding followed by excessive flexural cracking hampered the arching action activation for loads closer to the support. The comparison of experimental and calculated resistances using standard code-based expressions suggests that improvements in unitary shear capacity could be supported as a result of slabs' transverse load distribution capacity. Alternatively, increasing the effective shear width can help estimate one-way shear capacity for loads near to the support.@en

Several studies investigated the precision of non-linear finite element analyses (NLFEA) to predict the shear capacity of beams or the punching capacity of slab-column connections. However, in the literature, there is little discussion regarding the results of NLFEA to predict the ultimate capacity and failure mechanism of slabs susceptible to different failure mechanisms. In this study, a set of tests from literature that developed different shear failure mechanisms was evaluated by NLFEA. A total of thirteen slabs were modeled, where slab's width and shear span varied. A coupled damaged-plasticity model was employed to simulate the concrete behavior. The proposed model was calibrated to simulate specimens that failed as wide beams in one-way shear and specimens that failed by punching shear. Besides, the effect of different modeling choices was investigated: (i) the assumed stress–strain behavior in compression; (ii) tensile stress–strain behavior; (iii) the inclusion or not of damage parameters and (iv) the viscosity parameter. The results indicated that, on average, the proposed modeling strategy represented the failure mechanism and ultimate loads well. Also, the same calibrated model was found capable of representing one-way shear failure and punching shear failure or mixed modes. The sensitivity study demonstrated that the tensile stress–strain behavior and viscosity parameter influences the results of the numerical models more significantly than the assumed stress–strain behavior in compression or including/not including the damage parameters. This paper concludes that modeling strategies during the calibration process shall be checked carefully before performing any parametric analyses to identify the accuracy of the numerical models to represent the different failure mechanisms. Moreover, the validation step of the modeling strategy shall identify possible limits of the numerical model to be considered in the parametric analyses.

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One-way slabs under concentrated loads may fail by one-way shear, two-way shear, flexure, or a combination of these modes. This paper reviews shear and punching shear-failure mechanisms of one-way slabs under concentrated loads tested from the literature and investigates the accuracy of different approaches to predict the ultimate capacity for such slabs using the ACI code expressions. A database with 160 test results was evaluated. Shear and concentrated loads measured at failure were reviewed according to parameters such as the load position, slab width, and reinforcement ratios. The load position and slab width play a marked influence on the failure mechanism and tested loads. The analyses improved the understanding of the main parameters influencing the behavior of one-way slabs under concentrated loads. Finally, the proposed effective shear width expression enables accurate shear capacity predictions using the ACI code expressions.

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One-way slabs under concentrated loads may fail by one-way shear such as wide beams, punching shear, flexure, or by combining two or more of these mechanisms. Nevertheless, most publications have only addressed shear and punching failures without flexural reinforcement yielding. This study investigates the ultimate shear capacity of one-way slabs under concentrated loads with local reinforcement yielding. In total, 12 tests were conducted on six reinforced concrete slabs. Simply supported slabs of 1.60 m × 3.40 m × 0.15 m were tested. Three parameters were varied: the load position, the span length and the reinforcement ratio. All slabs failed initially by punching with limited or extensive reinforcement yielding. Due to the relatively large amount of transverse reinforcement (0.44 %), most slabs underwent a large shear redistribution around the load, resulting in a wide beam shear failure after the local punching failure. The test results were compared to the theoretical predictions of shear, punching and flexure capacity using code expressions and the Extended Strip Model (ESM). The ESM resulted in the closest predictions of the experiments. These experiments confirm that a brittle shear and punching failure mechanism can occur even after extensive reinforcement yielding. Moreover, the results indicate that the ESM can be used to assess one-way slabs under concentrated loads with local reinforcement yielding.

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Reinforced concrete one-way slabs under concentrated loads can develop different shear failure mechanisms: as wide beams in one-way shear, punching shear around the load or a mixed mode between them. Until now, most publications presented recommendations to assess the shear capacity considering only the one-way shear failure mechanism. This study proposed developing recommendations to assess both the one-way shear and punching shear capacity of such slabs. Different codes of practice were addressed, including the current Eurocode and fib Model Code 2010 expressions. The recommendations were validated against 143 test results from the literature. Following these recommendations, one-way shear and punching capacities predictions achieved enhanced and almost the same level of accuracy.@en

This study describes a set of recommendations to improve the precision of shear and punching shear capacity predictions for one-way slabs under concentrated loads, regardless of the governing failure mechanism, using the ABNT NBR 6118:2014 code provisions. For this purpose, a database of 143 test results was developed, including one-way slabs with different support conditions and loading layouts and that failed by different shear failure mechanisms: one-way shear, punching shear or a mixed mode. The key parameters influencing the load capacity and failure mechanism of these slabs were considered for the proposed recommendations: load position and slab width. Adjustments to the effective shear width definition and shear resisting control perimeter were described. Arching action for loads close to the support was also considered in both one-way shear and punching shear predictions. Considering the whole database and without separation by the failure mechanism, the ratio between tested and predicted resistances with the one-way shear expressions shows an average value of 1.22 and a coefficient of variation of 18.3%. The respective ratio between tested and predicted resistances with the punching shear expressions reached an average ratio of 1.23 with a coefficient of variation of 21.3%. Therefore, the proposed recommendations allow for reaching enhanced levels of precision in assessing the shear and punching shear capacity of one-way slabs under concentrated loads, regardless of the governing failure mechanism of the slabs.@en

One-way slabs under concentrated loads may fail by one-way shear, punching, flexure or a mixed-mode between them. This study examines the benefits of using Linear Elastic Finite Element Analyses (LEFEA) combined with analytical expressions to predict the shear and punching capacities of such slabs. Besides, the determination of the most critical shear failure mechanism is also addressed. A simplified approach is proposed to predict the shear and punching capacity without numerical models. Forty-eight tests of simply supported slabs under concentrated loads were evaluated. The LEFEA was conducted with ABAQUS. The analytical expressions are based on the Critical Shear Crack Theory (CSCT). The coupling of the CSCT-expressions with the LEFEA accurately predicts the governing shear failure mechanism and the shear capacity of most test results. In this study, it was also found that the punching capacity predictions may be improved by considering the influence of the slab width and load size on the governing failure mechanism. A similar level of precision was achieved using only analytical expressions when properly calibrated. Therefore, the CSCT expressions can be used at different stages of design and assessment of existing structures according to the Level of Approximation required.

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The outstanding mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC) can be used to improve the punching behavior of new slab-column connections. This study investigates the punching capacity of flat slab-column connections built with a rational combination of normal strength concrete (NSC) and UHPFRC in critical shear regions through non-linear finite element analyses (NLFEA) and by a punching shear model based on the critical shear crack theory (CSCT). Ten control tests from the literature were used to validate the Finite Element Models (FEM) developed to capture the behavior of slab-column connections made entirely with NSC, UHPFRC, and a combination of both materials. Parametric analyses were performed to investigate the behavior of connections with the rational use of UHPFRC, varying the reinforcement ratio, area, and thickness of the UHPFRC layer. The results indicated that placing a UHPFRC layer near the column in the slab compression zone significantly increases the punching capacity and deformation capacity compared to placing UHPFRC on the tensile side. The punching capacity enhancements varied between 26% and 156%, according to the reinforcement ratios and configurations of the UHPFRC layer investigated. The mean ratio between predicted punching capacities by advanced NLFEA and the analytical method proposed was 1.09, with a coefficient of variation of 10.3%. Therefore, the results indicated that the design of flat slabs with UHPFRC at the critical shear regions is a viable solution. Finally, the CSCT model can be used in design to predict the punching capacity of these connections.@en

The shear strength evaluation of reinforced concrete bridge deck slabs by accurate models can indicate strength reserves and avoid costly operations necessary for the extension of their lifetime. This article introduces an approach that extends the Critical Shear Displacement Theory model (CSDT) for reaching higher levels of approximation of the shear strength for slabs subjected to concentrated loads close to the support. A database with 141 tests of wide reinforced concrete members under concentrated loads close to the support failing in one-way shear was built. The tests represented typical loads in bridge slabs and were assessed through a combination of CSDT with different models of effective shear width. In other analyses, the entire database with 214 test results of slabs failing by different mechanisms was evaluated and a general effective shear width model was proposed (GESW). The best results, which are a function of the effective shear width model used, reached a mean ratio between experimental and predicted shear capacities of 1.06 with a coefficient of variation of 14%, which is similar to that reported by some studies including linear and non-linear finite element analyses. Furthermore, this level of accuracy was insensitive to the shear slenderness and support conditions of the tests. The extended CSDT predicted the shear capacity of bridge deck slabs in preliminary analyses more precise than semi-empirical models provided in the current design codes, and the level of accuracy is comparable to methods using Linear Elastic Finite Element Analyses (LEFEA). Moreover, our proposed combination of the CSDT with a general effective shear width model (GESW) provides reasonable levels of accuracy for slabs under concentrated loads regardless of the failure mode of the tests. Therefore, the proposed approaches can be applied to bridge deck slabs, which are subjected to a variety of loading and support conditions.

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Bridge deck slabs without shear reinforcement under concentrated loads close to line supports may develop different shear failure modes: (i) one-way shear by shear-compression or flexure-shear failure mechanisms and (ii) two-way shear or punching shear under asymmetrical loading conditions. Notably, most publications concentrate on one of the failure modes and do not delve into the transition between these failure modes. This study proposes to discuss the level of precision of the Critical Shear Crack Theory (CSCT) to predict the shear capacity of slabs subjected to transitional failure modes in shear due to asymmetrical load or support conditions. For this purpose, the CSCT models of one-way shear and two-way shear are coupled with Linear Elastic Finite Element Analyses (LEFEA) to evaluate the nonuniform distribution of shear forces and bending moments around the loaded area and on the control sections used. The use of LEFEA aids in understanding the change of failure modes according to parameters such as the member width to effective depth ratio and the shear span. The results indicate that the CSCT coupled with LEFEA allows for accurate predictions of the shear and punching shear capacity of slabs according to the governing failure mode of the tests. @en

The calibration of most analytical models that assess the shear strength of wide reinforced concrete members without shear reinforcement is based on simply supported beam tests, which may not be representative of slabs and wide members failing in shear. This paper addresses the knowledge on the shear strength of wide members, identification of their most important parameters, and an evaluation of the accuracy and precision of the main models presented in codes of practice and literature. A database of 170 shear tests was built on wide members loaded over the entire width, with the ratio width to effective depth b /d  > 1. This database includes members under concentrated loads (CLs) and distributed loads (DLs) in the span direction. A parameter analysis revealed such shear strength is mostly influenced by the shear slenderness and size effect rather than by the ratio b /d . Furthermore, the results show a clear decrease in the shear strength of continuous members under DLs to higher shear slenderness, similar to the behavior of members under CLs. This trend was well observed with the proposed model of shear slenderness, which assumes that continuous members with higher bending moment in the span than over the inner support behave closer to simply supported members. A comparison of the shear capacities predicted by the physical‐mechanical and semiempirical approaches showed the higher accuracy and precision of models based on the critical shear crack theory and critical shear displacement theory, regardless of the ratio b /d . Therefore, the same models derived based on beam tests are valid for wide members. Apart from that, the analyses of nonslender members with some strain‐based models combined with reducing factors of the acting shear load provide accurate results of shear strength for members without stirrups.@en

Most models of shear strength used to estimate the shear capacity of wide reinforced concrete members without shear reinforcement do not take into account the structural system or the support conditions. However, some experimental results indicate that bending moment can have a positive influence on members with predominant flexural action, contrary to most of the mechanical models governed by tensile strain in the control section. This indicates that the structural system or the support conditions can have an influence on the shear strength of wide members without shear reinforcement commonly neglected. In this paper, we investigate the influence of the structural system on the shear strength of wide members. For this purpose, we review the available test results that varied the structural system, and we compared the accuracy and precision level of shear strength models from the literature according to the structural system of the members. In the analyses, we observed that the ratio of tested to predicted shear capacity is 5 – 10 % smaller for cantilever members than for simply supported beams. On the other hand, the ratio of tested to predicted shear capacity is on average 10-20% larger in continuous members than in simply supported ones. Although these results may indicate some influence of the structural system in the shear behavior, in this study, we did not identify physical reasons to validate this hypothesis. In this way, this tendency of results could be addressed to some bias in the database. However, we verified that the correlation between the shear capacities of wide members could be better correlated with the shear slenderness by taking into account that the behavior of some continuous members under uniformly distributed loads is similar to the simply supported ones with a reduced span length.@en