| Summary: | © 2017 Taylor & Francis Group, London. In developing the constitutive model for steel fibre reinforced concrete, insight of the fibre behaviour in tension is vital. This paper reports on the behavioural observation of steel fibre reinforced concrete in tension using X-ray imaging. It is observed that crack paths find ways of minimum resistance; (i) through a section with poor fibre dispersion and/or (ii) divert around fibre ends, where possible. The results of X-ray imaging analysis are reviewed and statistical models for fibre dispersion are presented. Together, a revised fibre bond stress model in the Unified Variable Engagement Model is also proposed; taking into account the limiting maximum fibre volume percentage for which, beyond the limit, additional fibre content does not further improve the tensile performance due to the weaker cementitious matrix and crack paths are likely to divert around fibre ends.
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