Abstract:The beneficial effect of a composite material anchorage system (CMAS) upon the ductility and load capacity of reinforced concrete (RC) beams strengthened either with glass (GFRP) or carbon (CFRP) fabrics was investigated. The anchorage system consisted of U-shaped GFRP or CFRP strip (U-strip) at end of FRP. The U-strips were bonded around the beam section and further anchored by two tufts of glass fibres, each of them embedded at the opposite beam face and specifically in the region of compression zone of the beam web. Experimental evaluations in simply supported lightly reinforced concrete (RC) beams strengthened with one GFRP or a CFRP sheet anchored at its ends by the composite anchorage have shown that their bending capacity has increased by 8% and 17%, respectively, in relation to the capacity attained in similar RC strengthened beams without anchorage. On the other hand, their ductility was improved by an amount of 94% and 37%, respectively. ANSYS finite element program was also used to numerically verify the response of strengthened RC beams obtained experimentally. The numerical results obtained are in good agreement with the experimental, thus, the calibrated model could now be used to extend the experimental results at lower cost.

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Aims: The aim of this paper is to investigate the influence of the volume fraction of fibres, the depth of the beam and the shear span-to-depth ratio on the shear strength of steel fibre reinforced concrete beams. Background: Concrete is a material widely used in structures, as it has high compressive strength and stiffness with low cost manufacturing. However, it presents low tensile strength and ductility. Therefore, through years various materials have been embedded inside it to improve its properties, one of which is steel fibres. Steel fibre reinforced concrete presents improved flexural, tensile, shear and torsional strength and post-cracking ductility. Objective: A better understanding of the shear performance of SFRC could lead to improved behaviour and higher safety of structures subject to high shear forces. Therefore, the influence of steel fibres on shear strength of reinforced concrete beams without transverse reinforcement is experimentally investigated. Methods: Eighteen concrete beams were constructed for this purpose and tested under monotonic four-point bending, six of which were made of plain concrete and twelve of SFRC. Two different aspect ratios of beams, steel fibres volume fractions and shear span-to-depth ratios were selected. Results: During the experimental tests, the ultimate loading, deformation at the mid-span, propagation of cracks and failure mode were detected. From the tests, it was shown that SFRC beams with high volume fractions of fibres exhibited an increased shear capacity. Conclusion: The addition of steel fibres resulted in a slight increase of the compressive strength and a significant increase in the tensile strength of concrete and shear resistance capacity of the beam. Moreover, these beams exhibit a more ductile behaviour. Empirical relations predicting the shear strength capacity of fibre reinforced concrete beams were revised and applied successfully to verify the experimental results obtained in this study.