Shear fatigue behaviour of reinforced concrete elements without shear reinforcement

• We have proposed a shear fatigue model for RC elements without stirrups.
• Limitations of most important standards are firstly presented.
• Number of load cycles to diagonal cracking and residual strength can be predicted.
• We show that residual fatigue strength after diagonal cracking can be significant.

The shear fatigue behaviour of reinforced concrete elements without stirrups is dealt with in this paper. Existing experimental results have shown significant differences between the static and fatigue failure mode of reinforced concrete. It has been reported that beams without shear reinforcement designed to have a ductile failure in flexure are able to develop a brittle shear failure when they are subjected to repeated loads. Shear fatigue of reinforced concrete beams without stirrups is a complex process from the mechanical viewpoint that has not been fully understood yet. Typical shear fatigue failure takes place by inclination of a flexural crack in the shear span and its progressive propagation into the compression zone until its destruction when its depth is too small to resist the applied compression force. This process is analyzed in this paper by means of a mechanical model that helps in understanding the formation of a diagonal crack and its propagation with load cycles. The failure mode and residual strength after diagonal cracking are studied as a function of the stress state at the tip of the effective diagonal crack.