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• Plain and fibrous concrete were tested under three multiaxial stress state. • Strength and behaviour of concrete were analysed with respect to the stress ratio. • Failure modes of concrete under uniaxial and multiaxial stress state were compared. • Failure criterions of concrete under multiaxial stress state were proposed. This study involves the investigation of the effects of steel fibre content volume on the biaxial stress behaviour of steel fibre self-compacting concrete (SFSCC) at different stress ratios. This study covers compression-compression, compression-tension, and tension-tension stress regions. The results are discussed in terms of the uniaxial and biaxial strength, stress-strain relationship, and failure mode of SFSCC specimens. In terms of strength, 1.0% fibre volume fractions showed the highest increment in biaxial compression and compression-tension, which were 55% and 84%, respectively, when compared to plain concrete. This improvement was due to the integration of steel fibre. In contrast with compression strength, biaxial tension strength decreased in comparison to uniaxial tensile strength. Additionally, based on the octahedral stress space, the failure criteria of concrete for each region were proposed in a quadratic polynomial equation, and the parameters were derived from a regression analysis. [ABSTRACT FROM AUTHOR]

• The comparison between shallow recess and deep recess beam. • The substitution of bar reinforcement with the steel fibre reinforcement. • The influence of a v / d ratio in the failure mode of the beam half-joints. • Two semi-empirical equations were proposed based on the failure mode of beam. A complex geometry of precast reinforced concrete half-joint beams has resulted from the high shear force at the recessed ends of such beams. Immense levels of reinforcements are provided close to the re-entrant corner of these beams to prevent the propagation of diagonal cracks and sudden failure. However, this condition leads to reinforcement congestion and affects the bond between concrete and reinforcing steel due to improper concrete filling around the congested bars. Hence, the use of steel fibre self-compacting concrete (SFRSCC) was found to combine the advantages of eliminating the vibration works, and reduction of secondary reinforcement. An experimental study was conducted to examine the ability of 1.0% by volume of steel fibre to partially replace the traditional reinforcements on two types of half-joint beams (short recess (SR) and deep recess (DR) beams). Other factors taken into account is the variance in shear span values and nib height, as well as the ratio of shear-span-to-depth, a v / d. Observations showed that the replacement of 1.0% by volume of steel fibre volume fraction is possible only when substituting at least 50% of the vertical or horizontal reinforcement in SR beams. Meanwhile, the replacement over diagonal reinforcement is seemed to be not enough and the replacement is only promising in substituting part of stirrups in DR beams. The variance in the shear-span-to-depth a v / d ratio affects the shear failure mode of the beam half-joints. Two semi-empirical equations for predicting the shear strength of precast SCC and SFSCC beam-half joints are developed based on the analysis of failure modes. The first equation, which relies on the crushing of the concrete strut, was found to suit the SR beams, while the equation for DR beams suits the theoretical of reinforcement yielding. The two equations give a good correlation with the experimental results. [ABSTRACT FROM AUTHOR]