Fatigue Behavior of Shear-Critical Reinforced Concrete Beams

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The shear strength of Reinforced Concrete structures degrades under cyclic loading; leading to unforeseen, brittle shear failures. This thesis presents both experimental and analytical investigation to the fatigue behavior of Reinforced concrete beams failing in shear. The fatigue life of shear-critical beams is also discussed in light of the experimental and analytical output. An experimental research on six shear-critical Reinforced Concrete slender beams was conducted to investigate shear behavior under low-cycle fatigue loading. The variables were shear reinforcement ratio (0.00% and 0.13%) and type of loading (monotonic and one-side cyclic loading). All members fail in shear before yielding of longitudinal reinforcement as intended. The provision of only 0.13% of shear reinforcement significantly increased the capacity of the beam under monotonic loading by 51.93%. For beams with shear reinforcement, the load deflection response measured under monotonic loading provided an excellent envelope for cyclic response and shear strength degradation was significant with much reduced fatigue life in low-cycle fatigue ranges. Moreover, Strain measurements on shear reinforcements exhibited progressive increase in strain with each cycle confirming cyclic material softening of both the concrete and the stirrups. Surprisingly, a single beam with shear reinforcement under cyclic loading exhibited a higher capacity than its expected monotonic capacity. This has been attributed to alteration of diagonal crack path and possible favorable effects of fatigue loading are discussed.



shear-critical, low-cycle fatigue, diagonal crack path, slender beams