Title: Strength of Concrete under Multiaxial Stress States

Author(s): Kurt H. Gerstle, Diethelm L. Linse, Paolo Bertacchi, M.D.

Publication: Symposium Paper

Volume: 55

Issue:

Appears on pages(s): 103-132

Keywords: biaxial loads; compressive strength; concretes; deformation; mortars (material); strength; stresses; triaxial loads; triaxial stresses

DOI: 10.14359/6611

Date: 8/1/1978

Abstract:
Past investigations of the multiaxial behavior and strength of concrete have used both a wide variety of different materials, and of different test methods. In order to isolate the effects of these two variables, seven institutions cooperated in a test program in which mortar and concrete specimens were subjected to a variety of biaxial and triaxial compressive loading conditions, common to all participants. Identical materials were used in all tests, so that any systematic differences in the results could be attributed entirely to the differences in test methods. The effect of test method is predominantly a function of the specimen boundary conditions, which range from a specified stress boundary condition for perfectly flexible fluid cushion loadings, to a specified displacement boundary condition for perfectly rigid, rough platens. Mixed boundary conditions of various types occur with the use of conventional triaxial test cells, brush bearing platens, and lubricated loading plates. All of these loading conditions were represented in the program. Only strength results are presented in this paper. They clearly indicate the effects of surface constraints on the specimen; with increased boundary constraint, the ratio of multiaxial to uniaxial strength, as well as the ratio of cube to cylinder strength increases. Uniaxial, biaxial, and triaxial strengths of the materiaqs are compared by expressing them within a common octahedral normal-octahedral shear stress space. It appears possible to represent all observed failure points by a common compressive multiaxial strength criterion.