Shrinkage Effect on Shear Strength of Reinforced, High Strength Concrete Beams

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Title: Shrinkage Effect on Shear Strength of Reinforced, High Strength Concrete Beams

Author(s): R. Sato, H. Kawakane, T. Kawamoto, R. Ushio, and I. Maruyama

Publication: Special Publication

Volume: 246

Issue:

Appears on pages(s): 261-278

Keywords: equivalent tension reinforcement ratio; reinforced high strength concrete beams; shear strength; shrinkage; size effect

Date: 9/1/2007

Abstract:
Effect of autogenous shrinkage on the shear strength of reinforced high strength concrete beams is investigated, in which shear beams with the distance from compressive fiber to the centroid of reinforcing bars(effective depth) of 250mm, 500mm and 1000mm are prepared, made of high autogenous shrinkage- and expansive- or low autogenous shrinkage-high strength concretes with water to binder ratio of 0.23, respectively. The test results show that the shear strength at diagonal cracking of reinforced high autogenous shrinkage-high strength concrete beams is decreased by 5-18% compared with that of reinforced expansive- or low autogenous shrinkage-high strength concrete beams. Ultimate shear strength of the former is also lowered 20-45% than that of the latter, in which the differrences of the failure mode as well as the size effect are observed. Moreover, a new concept of the equivalent tension reinforcement ratio for the evaluation of the shrinkage effect on the shear strength at diagonal cracking is proposed, which is tension reinforcement ratio modified by considering the effect of tension reinforcement strain due to deformation of concrete at early ages. The concept shows succesfully the linear relationship between the shear strength at diagonal cracking and the effective depth to -2/5 power independent of the magnitude of the early age deformation of concrete, and a design equation for the shear strength at diagonal cracking applicable to concrete compressive strength from nearly 90-130N/mm2 is proposed.