Abstract
The effective utilisation of steel fibre reinforced concrete (SFRC) requires in-depth and detailed understanding of bonding mechanisms governing the tensile behaviour. In response to this demand, this study presents an empirical description of the axial force required to pull out a hooked end steel fibre from a cementitious matrix. It is based upon consistent experimental tests that show the force versus displacement plot is formed from a sequence of events in which partial and full debonding at the interface is followed by bending of the hook knee to raise the force to its maximum. A loss of peak force occurs with the reversed plasticity involved in a full straightening of the fibre that precedes the rapid sliding to its full removal under a falling force. The stages are assembled in the said order with a piecewise connection between linear segments and a curve of exponential decay. A power law can be introduced to describe the knee bending stage if preferred. The normalised co-ordinates were adopted for the simple mathematical discontinuous function of the full pull-out process. Normalising force and displacement for hooked fibre is based upon the maximum values found for straight fibre pull out. This would apply to an overall embedded length of unity and a unit peak force for a full debonding of straight fibre in similar materials. For hooked fibre the normalised co-ordinates given refer to the initiation and duration of each event to be tabulated at fractions of the embedded length with multiples of that force. Such predictions are seen to be in good agreement with average pull-out response curves.
Highlights
The development of steel fibre reinforced concrete (SFRC) marks a huge step forwards in building materials and construction technology, which is indispensable in the modern structural applications [1]
The effective utilisation of steel fibre reinforced concrete (SFRC) requires in-depth and detailed understanding of bonding mechanisms governing the tensile behaviour. In response to this demand, this study presents an empirical description of the axial force required to pull out a hooked end steel fibre from a cementitious matrix
This study aims to provide simple and conceptual method to predict the bonding mechanisms governing the pullout responses of straight and hooked end fibres
Summary
The development of steel fibre reinforced concrete (SFRC) marks a huge step forwards in building materials and construction technology, which is indispensable in the modern structural applications [1]. The consistency in the order of each stage promotes practical empirical description of the whole process within a discontinuous function It will be shown how an averaged experimental pull-out curve lends itself initially to a connection of linear segments describing bond breakdown and hook straightening. Some attempts to model the effect of fibre geometry on the pull-out response which have been made in recent years These models are restricted to a set of material properties and experimental boundary conditions. Their ability to provide an effective understanding of the bonding mechanisms is limited due to involving large number of parameters. This study aims to provide simple and conceptual method to predict the bonding mechanisms governing the pullout responses of straight and hooked end fibres
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