Masafumi WATANABE
Experimental Study on Size Effect of Deep Beam Focusing on the Diagonal Crack Propagation
Supervisor : Takumi SHIMOMURA
It is known that the shear capacity of reinforced concrete beams decreases with increase of effective depth. Especially, shear capacity of deep beams with small shear span ratio (a/d) is influenced by diagonal crack propagation and bearing condition of load point, and so on. Hence, experimental tests should be conducted on same conditions with homothetic specimens to consider the size effect of deep beams.
In this study, deep beams which a/d is 1.0 or 1.5 are loaded considering the bond of main reinforcements, the effective depth and bearing area as principal factors. As a result, if the diagonal crack is controlled by un-bonding the main reinforcement, shear capacity of beam specimens whose a/d is 1.5 was higher than normal beam specimens resulting in small size effect. On the other hand, shear capacity whose a/d is 1.0 does not depend on the bond of reinforcement. In this case, size effect was small regardless of bond condition. Furthermore, if the bearing stress is smaller than compressive strength of concrete, the propagation of diagonal crack is less encouraged. Therefore, the shear capacity of beam specimens is increased.
Consequently, the estimation method of shear capacity that considers the influence of size effect and a/d is proposed in this study
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