Stress-strain characteristic of SFRC using recycled fibres

This paper presents work from a comprehensive study on the development of a flexural design framework for concrete reinforced with steel fibres that are recovered from used tyres. The experimental flexural behaviour of notched concrete prisms reinforced with these fibres is initially presented. For comparison purposes, prisms reinforced with industrially produced fibres are also considered. An attempt to adopt an existing RILEM design framework to derive appropriate tensile stress-strain blocks is made, but problems are identified with key parameters of the framework. The influence of crack propagation and location of neutral axis depth on the tensile stress distribution is examined. Following an analytical study, it is concluded that the uniaxial stress-strain model, proposed by RILEM overestimates the load-carrying capacity and should be modified by utilising more advanced analytical techniques. © RILEM 2006

Shear behavior of prestressed precast beams made of self-compacting fiber reinforced concrete

Even after many years of in-depth research the shear behavior of concrete structures is still a subject for debate. Current Design Codes need to be adapted to new materials and production methods. This paper discusses some still unresolved doubts, based on an experimental program consisting of nine prestressed l-beams of different flange dimensions. Shear evaluation is analyzed in accordance with the Codes under different conditions: a combination of fibers with stirrups, the possible influence of flange width on shear strength and the interaction of fibers with other important parameters such as flange width and longitudinal reinforcement. The results obtained show that fibers act as additional reinforcement to stirrups and also that the Codes are within the safety limits as regards shear ultimate limit state (ULS). (C) 2013 Elsevier Ltd. All rights reserved.The authors of this work wish to thank the Research Bureau of the Spanish Ministry of Science and Innovation and Plan-E, for funding of Project BIA 2009-12722. We are also grateful for the collaboration of the precast manufacturer PREVALESA S.L.Cuenca Asensio, E.; Serna Ros, P. (2013). Shear behavior of prestressed precast beams made of self-compacting fiber reinforced concrete. Construction and Building Materials. 45:145-156. https://doi.org/10.1016/j.conbuildmat.2013.03.096S1451564

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

Critical analysis of fibre-reinforced polymer near-surface mounted double-shear pull-out tests

The study of the bond behaviour between fibre reinforced polymer (FRP) systems and concrete is an issue that nowadays attracts many researchers. The scientific community dedicated to the research of FRP reinforcement has been conducting numerous experimental programs aiming to assess the local bond-slip law of the FRP-adhesive-concrete connection. This paper reports the relevant results obtained by the Structural Composite Research Group of Minho University in the scope of an international Round Robin Test. The suitability of the recommended test setup to derive a local bond constitutive law for modelling the bond behaviour of Near Surface Mounted reinforcement systems is discussed based on a deep interpretation of the results. Keywords: Bond behaviour; Double-Shear pull-out test; Fibre reinforcedFundação para a Ciência e a Tecnologia (FCT