Investigating the Mechanism of Shear Fatigue in Reinforced Concrete Beams subjected to Pulsating and Moving Loads using Digital Image Correlation

Abstract

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.

Monitoring the Shear Fatigue Response of Reinforced Concrete Beams Subjected to Moving Loads using Digital Image Correlation

“…This contrasts with the hysteresis of Beam 2 which generally exhibits a rather close hysteresis (as the beam is loaded and then unloaded, it virtually returns to its original deflection value). Furthermore, the accelerated damage exhibited by Beam 3 at each load passage can also be attributed to the fact that as the applied load moves from Load Points 1 to 5, it has the effect of constantly changing the moment-toshear ratio (and hence the principal stress orientations at various locations along the beam) [23].…”

“…With regards to the pre-existing cracks, the change in principal stress orientations would cause shear stresses to develop across these cracks [23][24][25] and change sign as the load passes these cracks. It is anticipated that this crack shear reversal would cause two crack surfaces to slide against each other and widen thereby accelerating deterioration.…”

Fatigue Testing of Shear Reinforcement in Prestressed Concrete T-Beams of Bridges

“…This procedure accounts for the characteristics of older bridges and enables a more refined determination of the structural capacity. Independent of this German guideline and its refinement, research is currently being conducted all over the world on the load-bearing capacity of concrete bridges and individual structural parts, especially under fatigue loading [25][26][27][28][29][30][31][32][33][34][35].…”

Predicting the Flexural Response of a Reinforced Concrete Beam Using the Fracture-Plastic Model

“…After 28 days of moist curing, the beam was transferred to the test zone. Before testing, the surface of the beam was sprayed white and 50 mm square gridlines were prepared at the half span while the other half was manually marked with black random speckle pattern for [24][25][26]. Upon the preparation which took one day, the beam was finally tested using a rigid reaction frame.…”