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Shear Design of High-Strength Concrete Beams: A Review of the State-of-the-Art.

Shear Design of High-Strength Concrete Beams: A Review
of the State-of-the-Art.
(8195 K)

Duthinh, D.; Carino, N. J.

NISTIR 5870; 203 p. August 1996.

### Available from:

National Technical Information Service

Order number: PB96-214713

### Keywords:

building technology; compression field theory; design
codes; high strength concrete; reinforced concretes;
shear strength; strut and tie model; truss model

### Abstract:

*
This state-of-the-art review of the shear design of
high-strength concrete (HSC) beams consists of four
parts. In the first part, various analysis methods are
presented: a) The plastic solution assumes that both
concrete, modeled as a modified Mohr-Coulomb material
and steel reinforcement are at yield. Under shear
loading, the concrete web develops an inclined
compression field which satisfies both upper and lower
bound theorems. A plastic solution of shear friction is
also discussed. b) Both the compression field theory
and the modified compression field theory (MCFT) are
"exact" theories in the sense that they satisfy
equilibrium, compatibility of displacements and
stress-strain relationships. The MCFT accounts for the
contribution of the tensile strength of concrete to
shear resistance. c) Other "exact" solutions are also
discussed, that do not assume that the principal stress
and principal strain directions are aligned with each
other, as the MCFT does. d) the 45DG truss, the variable
angle truss (VAT) and strut-and-tie models (STM) belong
to a class of solutions that only satisfy equilibrium.
The second part of the report is a comparison of various
National Codes: a) The ACI Code is semi-empirical and
based on the 45DG truss with a correction term called the
concrete contribution. For shear-friction, the ACI Code
only accounts for a friction term. b) The Canadian Code
(CSA) and the AASHTO Code are more "rational" and based
on the MCFT. STM are acceptable for "D" regions near
supports, loads or sudden changes in geometry. For
shear-friction, the CSA Code accounts for a friction and
a cohesion term. c) The Norwegian (NS) Code's general
design method is also based on the MCFT. However, the
VAT method and a simplified method are also allowed.
Again, STM are acceptable for D regions. For
shear-friction, the Norwegian Code accounts for a
friction and a cohesion term. d) The Japanese Code is
based on an equilibrium theory and considers shear
resistance as a combination of arch action and (variable
angle) truss action. e) The CEB-FIP Code is based on
the VAT, and f) so is the French Prestressed Concrete
Code which includes a concrete contribution term. g)
However, the French Reinforced Concrete Code is based on
the 45DG truss with a concrete contribution term. The
third part of the report is a review of research
results: a) Beam test results are surveyed and compared
to various empirical and design code equations. b) Panel
tests are reviewed, that simulate the state of biaxial
tension and compression in beam webs. c) Shear friction
measurements and theories are discussed and d) Size
effect is briefly covered, with the help of fraction
mechanics. The last part of the report discusses future
work. We recommend that emphasis be placed on
experimental measurement of the shear friction
properties of HSC. Biaxial behavior is also important,
but would require a major commitment in funding. In
addition, we recommend that NIST perform a parametric
study of the strength of HSC beans, using the MCFT, to
determine the influence of various models of shear
friction and biaxial tension-compression softening; and
that the work on automation of strut-and-tie modeling be
expanded.
*