Finite solid circular cylinders subjected to arbitrary surface load. Part II - Application to double-punch test

This paper derives the stress distributions within a finite isotropic solid circular cylinder of diameter 2b and length 2h under the double-punch test, which was introduced by Chen (1970) for the determination of the indirect tensile strength of concrete. The stresses induced by the two rigid circular punches of diameter 2a at the top and bottom of the solid cylinder are modeled by considering contact problem. The general stress analysis discussed in a companion paper (Part I) is used to obtain the stress field within the solid. In general, tensile stress concentrations are developed beneath the punches compared to the roughly uniform tensile stress at the central portion of the axis of the cylinder. The maximum tensile stress in the tensile zone decreases with the increase of Poisson's ratio and a/b, but is roughly independent of h/b. For small Poisson's ratio (say about 0.1) and a/b (say smaller than 0.1), the assertion made by Chen (1970) and Marti (1989) that a uniform tensile stress field, similar to that of the Brazilian test, is developed along the axis of symmetry is incorrect. The tensile strength interpreted from the present analysis is found comparable to the formula proposed by Bortolotti (1988) for a/b > 0.2 and agrees well with the experimental data, and thus provides an improvement over Chen's (1970) original formula.