In light of recently published work highlighting the incompatibility between the concepts underlying current code specifications and fundamental concrete properties, the work presented herein focuses on assessing the ability of the methods adopted by some of the most widely used codes of practice for the design of reinforced concrete structures to provide predictions concerning load-carrying capacity in agreement with their experimentally established counterparts. A comparative study is carried out between the available experimental data and the predictions obtained from (1) the design codes considered, (2) a published alternative method (the compressive force path method), the development of which is based on assumptions different (if not contradictory) to those adopted by the available design codes, as well as (3) artificial neural networks that have been calibrated based on the available test data (the later data are presented herein in the form of a database). The comparative study reveals that the predictions of the artificial neural networks provide a close fit to the available experimental data. In addition, the predictions of the alternative assessment method are often closer to the available test data compared to their counterparts provided by the design codes considered. This highlights the urgent need to reassess the assumptions upon which the development of the design codes is based and identify the reasons that trigger the observed divergence between their predictions and the experimentally established values. Finally, it is demonstrated that reducing the incompatibility between the concepts underlying the development of the design methods and the fundamental material properties of concrete improves the effectiveness of these methods to a degree that calibration may eventually become unnecessary. Keywords Artificial neural network • Design codes • Ultimate limit state • RC beams • Compressive force path method • Physical models Abbreviations CFP Compressive force path ANN Artificial neural network ULS Ultimate limit state List of symbols a v Shear span b Beam width d Effective depth x Depth of the compressive zone A s Area of tensile reinforcement A s ′ Area of compressive reinforcement A sw Area of transverse reinforcement v ∕d Shear span-to-depth ratio f c Uniaxial compressive strength of concrete f yl Longitudinal reinforcement yield stress f yw Transverse reinforcement yield stress s Spacing between shear links l Ratio of tensile reinforcement (l = A s ∕b × d) t Ratio of compressive reinforcement (t = A s � ∕b × d) w Ratio of transverse reinforcement (w = A sw ∕b × s) V c Shear resistance of the RC beam without the contribution of the shear links V s Shear resistance offered by of shear links V u Shear developing along the span of the RC beam at failure M u Bending developing along the span of the RC beam at failure M f Flexural moment capacity of the cross section of the RC beam

A comparison of the predicted and experimentally-established behaviour of over 150 reinforced concrete beam specimens (selected from 465 test results considered) revealed that around 20% of the specimens exhibited shear failure rather than the expected flexural failure. The work presented in this paper investigated the possibility that the causes of shear failure reflected shortcomings of the code methods adopted for calculating flexural capacity. It was found that the predicted values of flexural capacity tended to underestimate their experimentally-established counterparts by up to 17% on average. It was shown that by accounting for the triaxial stress conditions invariably developing in the compressive zone through a simple modification of code-proposed stress blocks, the correlation between predicted and experimental values was similar to the best possible one resulting from the development and use of an artificial neural network model.

The behaviour of reinforced concrete beam-column connections under cyclic loading has been extensively investigated to date. A common feature of the results published is that, in contrast with current design objectives, connections are characterised by extensive cracking and large deformation before the plastic hinge formation within the linear elements. The present work describes an attempt to minimise cracking and deformation of the joints through the use of steel plates for anchoring the beam's longitudinal reinforcement and alternative reinforcement arrangements in the joint. The results obtained from tests on full-size beam-column subassemblages indicate a considerable improvement in behaviour, in spite of the significant reduction in reinforcement congestion.

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