Bond of reinforcing bars to steel fiber reinforced concrete

Steel fiber reinforced concrete (SFRC) has been increasingly used during recent years. Regarding bond of rebars to concrete, fibers provide passive confinement and improve bond capacity in terms of bond strength and, more importantly, toughness. An extensive experimental programme has been carried out, and SFRC specimens with embedded rebars have been subjected to the Pull Out Test to obtain the bond stress slip curves, retaining the bond strength and the area under the curve as measures of the bond capacity of concrete. The following parameters were considered: concrete compressive strength (30-50 MPa), rebar diameter (8-20 mm), concrete cover (between 30 mm and 5 times rebar diameter), fiber content (up to 70 kg/m(3)), and the slenderness and length of the steel fibers used. Predictive equations have been obtained to relate the experimental results to the factors considered, and the trends observed have been analyzed and discussed. (C) 2015 Elsevier Ltd. All rights reserved.The authors of this work wish to thank both the Research Bureau of the Spanish Ministry of Science and Innovation for the funding of the projects 'BIA 2009-12722' and 'BIA 2012-35776-AR', this research being a part thereof.García Taengua, EJ.; Martí Vargas, JR.; Serna Ros, P. (2016). Bond of reinforcing bars to steel fiber reinforced concrete. Construction and Building Materials. 105:275-284. https://doi.org/10.1016/j.conbuildmat.2015.12.044S27528410

Steel fibre reinforced concrete for elements failing in bending and in shear

Discrete steel fibres can increase significantly the bending and the shear resistance of concrete structural elements when Steel Fibre Reinforced Concrete (SFRC) is designed in such a way that fibre reinforcing mechanisms are optimized. To assess the fibre reinforcement effectiveness in shallow structural elements failing in bending and in shear, experimental and numerical research were performed. Uniaxial compression and bending tests were executed to derive the constitutive laws of the developed SFRC. Using a cross-section layered model and the material constitutive laws, the deformational behaviour of structural elements failing in bending was predicted from the moment-curvature relationship of the representative cross sections. To evaluate the influence of the percentage of fibres on the shear resistance of shallow structures, three point bending tests with shallow beams were performed. The applicability of the formulation proposed by RILEM TC 162-TDF for the prediction of the shear resistance of SFRC elements was evaluated. Inverse analysis was adopted to determine indirectly the values of the fracture mode I parameters of the developed SFRC. With these values, and using a softening diagram for modelling the crack shear softening behaviour, the response of the SFRC beams failing in shear was predicted.Fundação para a Ciência e a Tecnologia (FCT