NIST Time|NIST Home|About NIST|Contact NIST

HomeAll Years:AuthorKeywordTitle2005-2010:AuthorKeywordTitle

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


pdf icon 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.