Size Effect on Shear Behavior of Reinforced Concrete Beams with Shear Reinforcement
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Date
2019-11
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Addis Ababa University
Abstract
Past experimental researches showed that as the beam depth increases, there is a
significant decrease on the shear stress capacity of reinforced concrete beams without
shear reinforcement. This trend is called size effect. Since most beams contain at least
minimum shear reinforcement as required by building codes, it is also important to study
size effect on reinforced concrete beams with shear reinforcement. In this paper
experimental and analytical investigations were made to study size effect on shear
behavior of reinforced concrete beams with shear reinforcement. All parameters
influencing shear capacity of beam were held constant except beam depth and shear
reinforcement ratio. Six reinforced concrete beam specimens tested in laboratory and
twelve beam specimens analyzed by VecTor2 nonlinear finite element software.
Experimental results showed that for beams without shear reinforcement the shear stress
capacity decreased by 9.3%, on the other hand, for beams which have shear
reinforcement with ratio of 0.14% the shear stress capacity decreased by only 3.8%,
when the beam height raised from 240mm to 360mm. Analytical results also showed that
when depth of the specimen increased from 240mm to 1200mm, the shear stress capacity
decreased by 58.2% for beam specimens without shear reinforcement and by 48.9% for
beam specimens with 0.14% ratio of shear reinforcement. From both results it can be
concluded that even if using shear reinforcement minimize size effect, they cannot
eliminate size effect completely. The comparison made among experimental, code-based
and analytical predictions showed that Eurocode 2 and ACI 318-19 shear provisions
gave generally good estimates of shear capacity for al1 analyzed specimens. However,
the ACI 318-14 shear provision overestimate shear capacity of reinforced concrete
beams when depth of beams exceeds 800mm that is because it did not consider size
effect, so that, the decision made by ACI committee to replace it by new equation in ACI
318-19 which consider effect of member depth is correct.
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Keywords
Shear Reinforcement, Reinforced Concrete Beams, Shear Behavior