Sensitivity of Shear Strength of Reinforced Concrete and Prestressed Concrete Beams to Shear Friction and Concrete Softening According to Modified Compression Field Theory.
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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899