Model of Hooked Steel Fibers Reinforced Concrete under Tension

Abstract

The main objective of this research was to develop a model for predicting stress-strain relationship of hooked steel fibers reinforced concrete (HF-FRC) under tension. The research was divided into 2 parts. The first part was extensive tensile tests of HS-FRC. The hooked steel fibers having two plastic hinges at both ends were used. The size of tensile specimens was 5 x 5 cm in cross section and 50 cm in length. Parameters used in the study were: (a) L _f /D and L _f of the fibers (65/60, 65/35 and 80/60); (b) volume fractions of the fibers (0, 0.25, 0.5, 1.0 and 1.5%); and (c) compressive strength of concrete (30, 40 and 50 MPa). The main results obtained in test were stress-strain relationship of HS-FRC, first-peak strength, and post-cracking strength. The second part focused on statistical prediction. The basic model of stress-strain relationship was proposed in this research, i.e. linear relationship up to first-peak strength and assumed constant post-cracking strength. In statistical prediction, the dependent variables were first-peak strength and post-cracking strength of HF-FRC, while the independent variable were L _f /D, L _f , volume fraction of fibers, and compressive strength of concrete. A good prediction was obtained from the model, and the equations for using in the design were recommended. It was seen in the model that an increase in L _f /D ratio, L _f , volume fraction of the fibers, and compressive strength of concrete significantly enhanced the tensile performance of hooked steel fiber reinforced concrete, and could lead to high performance fiber reinforced concrete.