•The behaviour of stainless steel reinforced concrete beams is investigated.•A full and simplified version of a deformation-based design method is proposed and examined herein with reference to the ...current design rules in Eurocode 2.•A comprehensive parametric study is conducted to study the most influential parameters.•The serviceability limit state is also explored through a detailed analysis of the deflection behaviour.
Stainless steel reinforcement has become a very attractive option for reinforced concrete structures owing to its distinctive properties including outstanding corrosion resistance, excellent fire behaviour, long life cycle as well as low maintenance requirements. Additionally, stainless steel reinforcement offers exceptional ductility and strain hardening characteristics compared with other common materials, which are very desirable in design to avoid sudden collapse. However, most global design standards do not incorporate an appropriate design approach for reinforced concrete members with stainless steel. The substantial strain hardening characteristics of stainless steel are typically not represented in standardised material models and therefore this attractive characteristic is not exploited in design resulting in structural and economic inefficiencies. Hence, the aim of this paper is to propose and validate a new deformation-based design approach for stainless steel reinforced concrete beams based on the continuous strength method, with reference to the current design rules provided in Eurocode 2. This approach is shown to be an effective design tool that exploits the distinctive characteristics of stainless steel reinforcement in an efficient and reliable manner. It is shown to provide a more efficient design with less over-conservatism and greater accuracy, compared with other methods. A comprehensive parametric study is conducted using Abaqus software to study the influence that various geometric and material properties have on the capacity of the members. Moreover, the serviceability limit state is also explored through a detailed analysis of the deflection behaviour.
Abstract
In this paper the shear resistance of a member without shear reinforcement according to Eurocode 2 is investigated. This expression, as most expressions of design codes typically used to ...estimate the nominal shear resistance, has been created based on experimental investigations. It will be verified that in case of non-prestressed reinforced concrete member without stirrups, the shear resistance is carried by the shear resistance of the compressive zone; and the shear resistance given by the empirical expression of Eurocode 2 is actually the shear resistance of the compressive zone.
Knowing the mechanical background of the empirical expressions of Eurocode 2, the limits of its applicability can be shown, thus its error can be predicted. Using the reports of experimental investigations, it is easy to find cases to prove the correctness of the error-prediction. In this paper simple modifications will be suggested to Eurocode 2 shear design procedures, by which a more consistent level of safety can be ensured.
It has been recognized that the shear capacity of old bridges can play a crucial/key role in evaluating their structural safety. Determination of the shear capacity of critical cross‐sections ...presents a much greater challenge than the assessment of their bending capacity.
Due to abovementioned problems, the shear capacity of shorter reinforced concrete bridges with T‐beams has been evaluated with various models. Four different models were examined, the currently valid Eurocode 2, draft of the new version of Eurocode 2, the currently valid Eurocode 8‐3 and the model corresponding to modified compression field theory (MCFT). According to all the models, the capacity of deck of existing reinforced concrete bridge was calculated. This bridge was previously inspected and the actual amount and shape of the shear and bending reinforcement was determined.
The results obtained with different models were compared and the typical parameters which influence the shear capacity were analyzed. The results in terms of shear capacity show that different models can give quite different results for the same bridge.
•An effect of subsoil modelling on the test results in the case of footings subjected to punching.•The accuracy of the current and 2nd generation EC2 models for predicting punching capacity of the ...footings.•An effect of shear slenderness on punching shear capacity of the footings.•Post-punching resistance of the footings resting on the gravel cushion.
The results of an experimental program on the punching-shear capacity of foundation footings without shear reinforcement are presented and discussed in this paper, in the case of four tests on as many footings resting on a quasi-natural subsoil (top thin sand layer and bottom thick gravel layer). The design models of EC2 (2004) and prEC2 (2020) for the prediction of the punching-shear capacity are checked as well, by considering 90 tests well documented in the literature and the four tests performed in this research project. Special attention is devoted to the role played by the subsoil of the footing. The largest differences between the test results and the predictions occur in the case of quasi-natural subsoils, while the footings resting on point supports yield the smallest differences. The comparison of experimental and predicted capacities shows that the current model in EC2 (2004) is neither reliable nor safe, for any type of subsoil, since the ratio between the experimental and the assessed values of the load-bearing capacity ranges from 0.625 and 0.810 in 95% of the cases, depending on subsoil properties. On the contrary, the second-generation model introduced in prEC2 (2020) provides better results, since the previous ratio is close to 0.95 in 95% of the cases examined in the paper.
•Evaluation of systematic punching tests on shear-reinforced flat slabs with closed stirrups.•Constant concrete contribution independent of the shear reinforcement ratio according to ...EC2.•Presentation of two methods to determine the shear reinforcement contribution in flat slabs.•Evaluation of experimental results reveals a high degree of activation of the shear reinforcement.•Continuous decrease of concrete contribution with increasing shear reinforcement ratios.•Suggestion of a design approach based on a suspension strut-and-tie model.
The punching strength of flat slabs and footings without and with high amounts of shear reinforcement on the level of maximum punching shear capacity has been investigated extensively by various researchers over the last decades. The existing investigations suggest that the punching strength of RC slabs with shear reinforcement can be described by means of a contribution of concrete and a contribution of the shear reinforcement (steel contribution). However, a systematic evaluation of concrete and steel contribution depending on the amount of shear reinforcement has not yet been adequately possible since only few test series with low and medium amounts of shear reinforcement and a failure within the shear-reinforced zone have been available.
This lack of experimental data has been partly filled with eleven systematic punching tests on flat slabs and eleven further tests on footings conducted at RWTH Aachen University, Germany. In this paper, the development of the concrete and steel contributions in shear-reinforced flat slabs is investigated in detail and a method for calculating and analyzing both contributions is presented. The development of concrete and steel contribution depending on the amount of shear reinforcement is discussed and compared to the design provisions according to Eurocode 2, Model Code 2010 and the draft (of April 2018) of the next generation of Eurocode 2.
•The activation of punching reinforcement in flat slabs and column bases is analyzed.•The mechanical background of activation for next Eurocode 2 (prEC2) is explained.•An extended activation formula ...considering bond and anchorage is derived for prEC2.•Different types of shear reinforcement are considered on a uniform basis.•Focus is on transformation from a mechanical model to a simplified design formula.•The proposed activation formula is validated by systematic punching test results.
Various types of punching shear reinforcement have been developed during the past decades to increase the punching capacity and ductility of slab-column connections. Due to diverse geometries and thus varying anchorage conditions, the effectiveness of these elements contributing to total punching resistance can differ significantly. Generally, the degree of activation of shear reinforcement can be described by contributions of anchorage and of bond. Yet, most of current punching design provisions follow a simplified, empirical approach. Despite its mechanical background, the punching design according to the next generation of Eurocode 2 still does not consider the effect of better anchorage of, for example, double headed studs compared to simple stirrups.
In this paper, an extended activation formula for flat slabs as well as column bases is proposed as refinement for the next generation of Eurocode 2. This unifying approach considers different anchorage categories and thus enables more progressive design results. After discussing the background of possible activation scenarios, the effects of bond and anchorage in cracked concrete and the kinematic deformation behavior of slabs subjected to punching are identified as governing constraints. The major focus is on the transformation process from mechanical considerations to a simplified design formula to ensure practical applicability.
•Influence of recycled aggregates on the model uncertainty of Eurocode bond strength.•Recycled aggregates increase scatter and decrease bias of the model uncertainty.•Similar relative effect of ...recycled aggregate on pullout and lap splice bond strength.•Stochastic modelling of bond strength uncertainty for recycled aggregate concrete.•Calibration of partial factor for bond length design for recycled aggregate concrete.
This paper concerns the design of lap splice lengths for ribbed steel reinforcement bars embedded in concrete produced with coarse recycled concrete aggregates. Recycled aggregates are weaker and typically lead to concrete with lower tensile strength. Both aspects change the model uncertainty of bond strength formulae and a major topic of the paper is the influence of recycled aggregates on the model uncertainty of the bond strength model of fib Bulletin 72. A stochastic model for this model uncertainty is developed from a meta-analysis. The model uncertainty, estimated from analogue specimens made with either natural aggregate concrete or recycled aggregate concrete, is compared and the incorporation of recycled aggregates was indeed found to have a detrimental influence on the model uncertainty. A partial factor for lap splice length design is calibrated through reliability analyses so that the probability of failure of the bond length design of recycled aggregate concrete is equivalent to that of natural aggregate concrete. Two design equations were studied: that of the fib Bulletin 72 and that of the D6 draft of the second generation of Eurocode 2.
•A comparison of current punching design provisions reveals major differences.•Systematic punching tests are used to determine the concrete and steel contribution.•In shear-reinforced column bases, a ...decreasing concrete contribution is observed.•A high degree of activation of the shear reinforcement (~0.8∙fyw) is identified.•A ‘suspension’ strut-and-tie model with variable concrete contribution is suggested.•The next generation of Eurocode 2 provides the most progressive design results.
The punching shear capacity of reinforced concrete flat slabs and column bases without shear reinforcement as well as with failure on the level of maximum punching strength has been analyzed extensively in the past. For shear-reinforced slabs, most punching shear models follow an additive approach assuming a combination of a contribution of concrete and a contribution of shear reinforcement (steel contribution). However, a systematic evaluation of concrete and steel contributions depending on the amount of shear reinforcement has not yet been adequately possible since only a few test series with low and medium amounts of shear reinforcement investigating the failure within the shear-reinforced zone have been available.
In this paper, the development of concrete and steel contributions in shear-reinforced column bases is investigated in detail based on eleven punching tests with systematically varying shear reinforcement ratios. Significant differences between various punching design approaches regarding the interaction of concrete and steel contributions are revealed and a new method for evaluation is presented. The development of both contributions depending on the amount of shear reinforcement is discussed and compared to the design provisions according to Eurocode 2, Model Code 2010 and the draft for the next generation of Eurocode 2 which has been undergoing an optimization process in recent years.
New design provisions for anchorage and lap design, based on Model Code 2010 and the related background document, have been proposed for the next generation of Eurocode 2 (prEC2). In this article, ...the new provisions are examined and compared with the provisions in current Eurocode 2 (EC2). In the first of the three parts of this study, design examples are developed to show the practicability and effectiveness of the new design provisions. In the second part, parametric studies are carried out to check the generality of the new provisions and to clarify the roles of the main input parameters controlling the design of anchorages and laps. In the third part, a comparison is made between the predictions based on the new provisions and the results of a large database reported in the literature. To improve the fitting of the test results, adjustments are proposed for the coefficients appearing in the provisions of prEC2. The proposed adjustments—that may be introduced into National Annexes—ensure a sufficient level of safety of the new provisions for the design of anchorages and laps.
•Database of experimental results on recycled aggregate concrete beams compiled.•Database filtered by different parameters—concrete strength, anchorage, etc.•Database analyzed to identify clear ...failure types—flexural or shear.•Sub-databases formed for flexural and shear failure (with and without stirrups).•Applicability of Eurocode 2 provisions to recycled aggregate concrete beams tested.
A comprehensive database of recycled aggregate concrete and companion natural aggregate concrete beams’ flexural and shear strength was compiled from 217 experimental results. Strict criteria were applied to determine the failure type. Sub-databases were formed with beams failing in flexure and shear with and without stirrups. On each sub-database the applicability of Eurocode 2 provisions for flexural and shear strength to recycled aggregate concrete beams was tested. The results show that flexural and shear strength of recycled aggregate concrete beams without stirrups is successfully predicted by Eurocode 2. As for beams with stirrups, further research and experimental results are necessary.
PDF
