An experimental investigation on three shear-critical reinforced concrete beams was performed to investigate the mechanism of shear fatigue. The first beam was simply tested to failure under monotonic loading to determine the static capacity, whereas the other two were subjected to repetitive loading below its static capacity to failure. Of these two beams, one was subjected to a stationary pulsating load at midspan while the other was subjected to a step-wise moving load along the span. During each experiment, the crack pattern was monitored throughout using an automated crack mapping employing the digital image correlation technique. The results show that each beam exhibited a unique crack pattern which could be characterised as shear-flexure in nature. It is shown the nature of crack propagation under monotonic loading is dissimilar to that under repetitive loading, especially when the load is not stationary. Moving load is also shown to cause greater damage to the beam than the stationary pulsating load and result in a reduction in fatigue life by almost two orders of magnitude.

A series of three reinforced concrete beams without shear reinforcement were tested to failure under a centre-span monotonic load, a centre-span pulsating load, and a stepwise-moving pulsating load. During each experiment, load-deflection response was continuously monitored and at several stages during the experiment, the load was briefly stopped for crack observations. In addition to this manual crack mapping, more detailed crack mappings were undertaken using the digital image correlation (DIC) technique, employing the open-source DIC software Ncorr. It was shown that while the three beams exhibited a similar mode of failure (i.e. shear), each beam displayed a rather distinctive overall behaviour, particularly with regard to the load-deflection response and the nature of crack initiation and propagation. Results from the DIC analysis are presented to provide direct evidence on the damage progression during the load cycles and discuss the reduced fatigue life exhibited by the beam subjected to stepwise-moving pulsating load