Abstract
Cohesion is defined as the shear strength of material when compressive stress is zero. This article presents a new method for the experimental determination of cohesion at pre-set angles of shear deformation. Specially designed moulds are created to force deformation (close to τ-axis) at fixed pre-set values of angle with respect to normal stress σ. Testing is performed on series of concrete blocks of different strengths. From the compressive side, cohesion is determined from the extrapolation of the linear Mohr–Coulomb (MC) model, as the intercept on the shear stress axis. From the tensile stress side (from the left), cohesion is obtained using the Brazilian test results: first, indirect tensile strength of material σtBT is measured, then Mohr circle diagram values are calculated and cohesion is determined as the value of shear stress τBT on the Mohr circle where normal stress (σ)t = 0. A hypothesis is made that cohesion is the common point between two tests. In the numerical part, a theory of ultimate load is applied to model Brazilian test using the angle of shear friction from the MC model. Matching experimental and numerical results confirm that the proposed procedure is applicable in numerical analysis.
Highlights
In order to describe the deformation behaviour of brittle material, complex issues are discussed for the Brazilian test and forced shear test
Load deformation curves obtained with finite element method (FEM) model showed remarkable matching with approximately
This paper presents a new method of experimental approach to the cohesion determination from nonlinear material analysis: Young’s modulus E, Poisson’s ratio ν, cohesion c and angle of internal the shear stress axis with tests at pre-set values of the deformation angle
Summary
In order to describe the deformation behaviour of brittle material, complex issues are discussed for the Brazilian test and forced shear test. Chen [16] justified the assumption that concrete can be considered as perfectly plastic material applicable for certain classes of problems in mechanics. He described the argument as an “idealisation which contains the essential features of certain material behaviour: the tangent modulus when loading in the plastic range is small compared with the elastic modulus, and the unloading response is elastic. Cohesion and angle of friction are determined from tensile strength and uniaxial compression [22]. Mohr–Coulomb model to different types of concrete and used cohesion parameters to describe the concrete softening/hardening and accumulative plastic deformations [24,25,26,27]
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