Bond behaviour of high-strength steel bars in concrete with steel fibres

Reductions in materials consumption through the use of high-strength materials is important in building construction. However, high-strength steel applications have possible challenges such as their effects on bond behaviour and structural ductility. The bond behaviour, total energy capacity and failure modes of headed and straight high-strength and normal-strength steel bars were investigated using pull-out tests. In the experimental programme, 48 concrete specimens with a compressive strength of 40 MPa, different ratios of steel fibres and embedded steel bars with different yield strengths were subject to pull-out tests. The results showed that the headed bars had far greater bond stress and total energy capacity than the straight bars. It was also found that the higher the yield strength of the bars, the higher the energy capacity and bond stress. Although increases in fibre ratios led to increases in energy capacity, they did not absolutely increase the bond stress. The specimens with both headed and straight bars failed by splitting.