Fatigue Behavior of Shear-Critical Reinforced Concrete Beams
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Date
2018-03-21
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AAU
Abstract
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.
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Keywords
shear-critical, low-cycle fatigue, diagonal crack path, slender beams