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Sensitivity of Shear Strength of Reinforced Concrete and Prestressed Concrete Beams to Shear Friction and Concrete Softening According to Modified Compression Field Theory.


pdf icon Sensitivity of Shear Strength of Reinforced Concrete and Prestressed Concrete Beams to Shear Friction and Concrete Softening According to Modified Compression Field Theory. (1481 K)
Duthinh, D.

ACI Structural Journal, Vol. 96, No. 4, 495-508, July/August 1999.

Keywords:

reinforced concretes; concrete beams; aggregates; compressing; prestressed concretes

Abstract:

The modified compression field theory (MCFT) is used to study the effect of shear friction and biaxial softening on the computed shear strength of reinforced (RC) or prestressed concrete (PC) beams. A comparison is presented of the various relationships that have been proposed to represent the shear friction behavior of cracked reinforced concrete. A decrease in shear friction within the range of experimental data as found, for example, in high-strength concrete, can lower the shear strength of beams with minimum shear reinforcement by 15 to 25 percent, according to the MCFT. In addition, a comparison is presented of different relationships used to represent the biaxial compression-tension strength of reinforced concrete for RC and PC beams. Some theories of biaxial softening of concrete do not predict concrete crushing even for very high deformations, but rather show significant shear force gain after stirrup yielding and crack slipping. For the RC beam example, some theories predict shear tension failure while others predict diagonal compression failure. However, the first peaks of shear load, which occur close to stirrup yielding and crack slipping, are within 10 percent of one another for the various theories and within 10 percent of the test value for the PC beam.