Fatigue Behavior Evaluation of Concrete Beam under ۴-Point Bending Cyclic Loading

Rocks in engineering projects are subjected to cyclic disturbances such as earthquakes, underground construction activities, and underground gas storage in caverns. However, the response of brittle materials to cyclic loading is not unique. Consequently, evaluating the mechanical properties and fatigue behavior of rocks holds significant importance in engineering designs. This study focuses on subjecting a collection of cubic concrete samples, categorized into three groups with distinct mechanical properties, to both monotonic and cyclic four-point bending loading. Three groups of cubic concrete samples with different mixing designs were prepared to evaluate the effect of the mechanical strength of the samples on the fatigue response of the rock, in such a way that: The first group (A) with ultimate compressive strength (UCS): ۱۹ MPa, the second group (B) with (UCS): ۴۹ MPa, and the third group (C) with (UCS): ۷۱ MPa. Experimental results show that the cyclic failure strength, due to the presence of damage and fatigue phenomena, has decreased relative to the monotonic loading. Also, the cyclic fracture toughness ( ) has decreased by ۸%, ۵%, and ۶% relative to the monotonic fracture toughness ( ) for the three groups of (A), (B), and (C), respectively.