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Strengthening reinforced concrete (RC) beams in shear using carbon fibre-reinforced polymer (CFRP) has been found to enhance, significantly, the shear capacity of existing RC beams. In previous studies the use of steel plates bonded externally to the RC beams was found to improve the shear performance of these beams. Most of the previous work was conducted on RC beams having rectangular sections. The main objective of this paper is to gain a better understanding and enhance the experimental database of shear behaviour of RC T-beams strengthened with externally bonded reinforcement (EBR) systems. The present study encompasses some of the important parameters such as direction of EBR fibre alignment and the strengthening materials made of carbon-fibre sheets, steel plates or steel bars for shear strengthening. The contribution of EBR to the shear capacity of the T-beams was computed using three design codes and compared with the experimental output. A series of RC T-beams was tested experimentally with the CFRP and steel strips carefully aligned and spaced. A reference T-beam and a rectangular beam were tested as well to explore the effect of the internal shear reinforcement and the existence of the flange on the shear capacity of the beam. [ABSTRACT FROM AUTHOR]

The flexural response of reinforced concrete (RC) beams exposed to fire is investigated in this paper. A macroscopic finite element model, capable of tracing the behaviour of RC beams from pre-fire stage to collapse in fire is used in the analysis. The model includes the three stages associated with fire resistance analysis, namely establishing the fire temperature-time development, calculating the heat transfer through the structure from fire and the structural analysis. The model is applied to investigate the effect of six parameters, namely the fire scenario, load level, concrete cover thickness, aggregate type, failures criteria and span length on the fire response of RC beams. Through the results of the parametric study, it is shown that the type of failure criterion, load level, fire scenario, concrete cover thickness and aggregate type have significant influence on fire resistance of RC beams. It is also shown that, while the span length has significant influence on the overall fire behaviour, it has a minor effect on the fire resistance of RC beams. [ABSTRACT FROM AUTHOR]

Member analysis is the main verification method adopted for reinforced concrete (RC) beams by most codes. The verification by means of member analysis consists of comparing the design forces (bending moment, axial force and shear force) with the resisting forces, where the former are computed at ambient temperature and the latter are evaluated using simplified methods considering the prescribed fire duration. The main objection that might be raised against member analysis is that, by computing the design forces at ambient temperature, indirect actions arising in the structure owing to thermal expansion are not taken into consideration; the time-dependent response of the structure is also neglected. In this paper, the behaviour of a set of fixed-end rectangular beams with varying axial restraints is discussed. The results are used to illustrate a simplified plastic verification procedure that allows determination not only of the load-carrying capacity of the beams, but also evaluation of the deflections for any given fire duration. [ABSTRACT FROM AUTHOR]

The new Svinesund Bridge is an arch motorway bridge on the border separating Norway and Sweden. The arch is a single, centrally located concrete structure with a span of 247.3 m, which is believed to be the longest span for a single free-standing concrete arch in the world. The bridge decks consist of two steel orthotropic boxes, one on each side of the arch and connected by cross beams. The total length of the bridge is 704 m between abutments. The design is the winning concept of an international competition. The bridge was opened to traffic in 2005, and received the fib Award for Outstanding Structures, Special Mention, in 2006. [ABSTRACT FROM AUTHOR]

The article proposes a model of corroded reinforced concrete behavior of the structural elements. The CEB-FIB model code allows the quantification of the coupled effect of the steel cross-section reduction and the loss of the steel-concrete bond on deflection of reinforced concrete beams under service loads. Meanwhile, an environmental-damage variable is introduced into the steel-concrete bond relationship to take into account the slip between the steel and the concrete.

The shear strength of reinforced concrete beams with stirrups has been a highly controversial matter since Ritter and Mörsh proposed the first truss models. Since then, different analytical models have been discussed, such as truss models with concrete contribution, shear/compression theories, truss models with variable angle of inclination, and compression field theories. However, some of these models were too complex to be implemented in a code of practice and they had to be simplified. As Regan has pointed out, for simpler models the problem is mostly that of the need to neglect some factors, considered secondaries. However, what is secondary in one case may be primary in another.With the release of the new Eurocode 2 (prEN 1992-1-1:2003) the controversy has been raised again. The EC-2 proposes a very simple formulation based on a truss model. However, the authors think that it is a gross oversimplification of a complex problem as it neglects important key variables. In this paper the new EC-2 shear procedure predictions are compared to empirical tests and to other simplified formulations. It is concluded that the EC-2 procedure is very easy to use by practising engineers but it presents a great scatter of results. On the one hand, it may be too conservative for slightly shear-reinforced beams or for prestressed beams. On the other, it may be slightly unconservative for heavily reinforced members. [ABSTRACT FROM AUTHOR]

A total of twelve partially prestressed concrete T-beams were cast without and with fibres in partial and full depth. These beams were tested to assess the effect of fibre addition in different zones in the cross-section, namely, flange, web or the entire cross-section, on the load-deflection performance of the flexure critical beam specimens. An attempt has been made to predict the load-deflection characteristics of the beam specimens utilising the tension softening effects in the stress-strain behaviour of fibre-reinforced concrete. The proposed model accounts for the interaction of the matrix with the fibre pull-out mechanism. The details of the constitutive material properties used and the proposed layer-based analysis are presented in this paper. Comparisons with test data show good agreement. [ABSTRACT FROM AUTHOR]

Moment redistribution has traditionally been considered as an ultimate limit state (ULS) phenomenon closely linked to considerations of reinforcement ductility. This paper demonstrates that a significant proportion of this redistribution will frequently occur at the serviceability limit state (SLS) because of the mismatch between the flexural stiffness assumed when calculating moments for the ULS and those actually occurring at the SLS owing to variations in the reinforcement layout along the member and the influence of cracking. This was demonstrated by tests on 37 two-span beams, the parameters investigated being values of redistribution, beam depth, reinforcement arrangements, concrete strength and the effect of brittle reinforcement. The results showed that there is scope for increasing the permissible limits for redistribution from supports into adjacent spans beyond those currently prescribed in design codes. This was supported by numerical modelling. However, considerations of crack width and reinforcement yield at the SLS may be limiting factors. Caution is advised if redistribution from the spans back to the supports is intended since it may prove difficult in practice to achieve the levels of redistribution anticipated in the design. [ABSTRACT FROM AUTHOR]

The strength and ductility of high-strength concrete (HSC) beams are enhanced through the application of helical reinforcement located in the compression region of the beams. The pitch of the helix is an important parameter controlling the level of strength and ductility enhancement of over-reinforced HSC beams. This paper presents an experimental investigation of the effect of helix pitch on the beam behaviour by testing five helically confined, full-scale beams. The helix pitches were 25, 50, 75, 100 and 160 mm. The cross-section of the beams was 200 × 300 mm, and with a length of 4 m and a clear span of 3·6 m subjected to four-point loading, with emphasis placed on the midspan deflection. The main results indicate that the helix had negligible effect when the helical pitch was 160 mm (helix diameter), the concrete cover spalling-off load increased linearly as the helical pitch increased, and the ultimate load decreased as the helical pitch increased. [ABSTRACT FROM AUTHOR]

In order to grasp the shear strength of a precast segment structure with external tendons, shear tests were carried out on nine different cantilever beams. The parameters were in situ concrete or precast segment, internal and external prestressing, and shear keys. This paper presents the results of these tests and proposes a new formulation to estimate the shear strength of a precast segment beam using external prestressing. [ABSTRACT FROM AUTHOR]

This paper discusses the influence that two types of drilling fluid, bentonite and a polymer, have on the bond capacity of reinforcement bars that are cast in concrete placed under them. Test results from both laboratory specimens and site tests are discussed and the results compared to capacities predicted by various codes. It is shown that Eurocode 2 predicts the bond capacity of bars in concrete cast under bentonite well, providing the assumption of poor bond conditions is made. The results for bars in concrete cast under polymers are less clear and there appear to be significant differences between the performance on site and that in the laboratory. [ABSTRACT FROM AUTHOR]

Tests were conducted on eight reinforced concrete hollow beams subjected to combined load of bending, shear and torsion. The beams were designed using the direct design method that was discussed in Part I. All beams had an overall cross-section dimension of 300 × 300 mm with a wall thickness of 50 mm. The overall length of the beam was 3800 mm. The two main variables in the series were the ratio in the web of the maximum elastic shear stress due to twisting moment to elastic shear stress due to shear force which varied between 0.59 and 6.84, and the ratio of the maximum twisting moment to the bending moment which varied between 0.19 and 2.62. The beams were experimentally tested in the University of Glasgow, Scotland, UK. Good agreement was found between the design and experimental failure loads. All beams failed near the design loads and had undergone ductile behaviour until failure. The results indicate that the direct design method can be successfully used to design reinforced concrete box beams for the combined effect of bending, shear and torsion loads. [ABSTRACT FROM AUTHOR]

This paper, Part I, presents a general `direct design procedure' for the design of reinforced concrete hollow beams subjected to a combined load of bending, shear and torsion. Elastic stress field in conjunction with Nielsen's two- dimensional yield criterion for reinforced concrete subjected to in-plane forces were used in the design of reinforcement. This procedure is based on and satisfies the lower bound theorem of the classical theory of plasticity. The main features of this procedure are the precluding of the use of empirical equations as is the case with existing codes of practice and in addition to satisfying the requirements of the theory of plasticity it reduces the ductility demand assumed by this theory. Comparison between the direct design procedure and the truss analogy showed that the direct design procedure leads to steel requirements close to those of the truss analogy when the angle of inclination of the struts is 45°. The direct design procedure produced much less reinforcement than the American Concrete Institute and the British Standards Institute codes. [ABSTRACT FROM AUTHOR]

This paper describes an experimental study on the flexural ductility of high-strength concrete beams. Nineteen isostatic beams, simply supported, were tested in the course of this work. Two symmetrical concentrated loads were applied to the beams at intervals of approximately one-third of the span. Ductility was studied by defining certain parameters, which have been termed ductility indexes. The main variables in this study are the compressive strength of the concrete and the longitudinal tensile reinforcement ratio. The results of the tests are examined and discussed, and some conclusions are drawn. The test results were compared with recommendations suggested by codes of practice and again conclusions are drawn. [ABSTRACT FROM AUTHOR]

Evaluating the ductility of reinforced concrete beams is essential in order to avoid a fragile collapse of the structure by ensuring an adequate deformation at ultimate load. This paper presents a theoretical model for the calculation of plastic rotation. Results obtained are compared with those obtained from an experimental programme in which a set of beams were tested to failure. From the comparison, a good agreement between theoretical and experimental results was achieved. The proposed theoretical model considers the influence of certain factors: steel properties, concrete strength, section depth, and the tension stiffening effect. Concrete strength, particularly, is an interesting parameter since for high-strength concrete, the ultimate concrete strain, ϵcu, decreases as the concrete strength increases. [ABSTRACT FROM AUTHOR]

Results of an experimental study on 21 fibre reinforced concrete beams indicate that steel fibres do not only increase shear capacity but also provide substantial post-peak resistance and ductility in conventionally reinforced beams as well as in prestressed pretensioned concrete beams. The tests were carried out on 2 m long beam specimens reinforced with longitudinal bars and fibres. Test variables were amount and type of fibres, amount of stirrups and type of longitudinal reinforcement (prestressed or non-prestressed). [ABSTRACT FROM AUTHOR]

A correction is presented to the name of the second author that was published in the article "Response of cracked simply supported concrete beam with moving vehicle load" who is namely Zhao Liu.

A table of contents for the issue is presented which discuss topics including concrete beams, tensile strength and shear wall.

A table of contents for the issue is presented.

The article lists topics within the journal including shear tests on continuous prestressed concrete beams, non-linear finite element analyses of large reinforced concrete structures and blast resistance characteristics of concrete.

The article lists several articles to be featured in the next 2014 issue of the journal "Structural Concrete," including "Influence of time-dependent effects on the crack spacing in reinforced concrete beams," by Arnaud Castel and Raymond Gilbert, "Consistent practical design of concrete structures," by Bente Nyhus, and "Modeling, verifications and investigation on behavior of circular CFST colums," by Pramod Gupta, Ziyad Khaudhair and Ashok Ahuja.