An experimental study on the failure modes of high strength concrete beams with particular references to variation of the tensile reinforcement ratio

• The behaviour of reinforced HSC beams is elastic.
• Increase of tensile reinforcement ratio makes more cracks with lower height and width.
• Moment curvature, load deflection curves act inelastic once tensile reinforcements yield.
• Mentioned curves perform elastic before yielding of tensile reinforcements.

For many years, high-strength concrete (HSC) has been used in high-rise buildings and bridges. The primary reasons for selecting HSC are to produce a more economical product, provide a feasible technical solution, or a combination of both. Despite a lot of advantages in the usage of HSC, it exhibits a brittle failure in comparison with normal strength concrete (NSC). For a comprehensive discussion on the failure of HSC beams, a total of six full scale reinforced HSC beams have been designed based on ACI code provisions and cast with compressive strength in the range of 65 MPa ⩽ fc′ ⩽ 75 MPa and tested under two-point top loading. The general behaviour of tested beams has been investigated with observation on mid span deflection, failure mode and crack growth. Increase of the tensile reinforcement ratio results in more cracks but with lower height and width. The linear graphs between the applied load and corresponding deflection or curvature in reinforced HSC beams showed that the behaviour of these beams is elastic and any increase in the tensile reinforcement ratio results in an increase in the ultimate load too. The moment–curvature graph and load–deflection curve started with an initial elastic response followed by an inelastic behaviour that appears with a gradual decrease in stiffness till the ultimate moment is reached.