Abstract
The effect of both size specimen and boundary conditions on the splitting tensile strength, determined from the Brazilian test, were studied experimentally. A total of 110 splitting tests of granite and mortar specimens were performed, using cylindrical and prismatic specimens of sizes between 17 mm and 300 mm. To analyze the effect of the boundary conditions, the specimens were tested with different widths of load bearing strip in the range of size recommended by the standards. The influence of the rupture mode (stable or unstable crack propagation) on the splitting tensile strength was also explored. The results of the tests were compared with the theoretical predictions obtained from a closed form analytical expression based on the cohesive crack model. The validity of the classical limit strength theory for larger size specimens was also analyzed. The results indicate that the splitting tensile strength depends strongly on specimen size and on the boundary conditions of the test. As the size of the specimen increases and the relative width of the bearing strip decreases, the splitting strength tends asymptotically to the minimum value coincident with the tensile strength. The dependence of the Brazilian test on the specimen size and boundary conditions closely follows the predictions of the cohesive crack model.
Résumé
L'influence de la taille et des conditions de bords sur la résistance mécanique à la traction indirecte (essai brésilien) ont été déterminés à partir des essais de compression diamétrale. On a essayé un total de 110 éprouvettes, en granite et en mortier. Les échantillons employés étaient prismatiques et cylindriques, de dimensions comprises entre 17 mm et 300 mm. Afin d'analyser l'effet des conditions d'essai, les échantillons ont été testés avec différentes largeurs d'appuis, dans l'intervalle conseillé par la norme. L'influence du mode de rupture (propagation stable ou instable) sur la résistance mécanique à la traction a été aussi testée. On a comparé les résultats des essais avec les prévisions théoriques obtenues moyennant une expression analytique fermée qui s'appuie sur le modèle de la fissure cohésive. La validité de l'approche de la contrainte limite a été analysée pour des éprouvettes de plus grande taille. Les résultats montrent que la résistance à la traction des éprouvettes est étrotement liée à la taille et aux conditions de l'essai. Quand la taille de l'éprouvette augmente et la largeur relative de l'appui diminue, la résistance atteint une limite qui correspond à la résistance à la traction. L'essai de compression indirecte (essai brésilien) dépend de la taille de l'éprouvette et des conditions de l'essai, en accord étroit avec les prévisions du modèle de la fissure cohésive.
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Editorial Note Prof. M. Elices and Prof. J. Planas are RILEM Senior Members. Both participate in the work of RILEM Technical Committee QFS (Size effect and scaling of quasibrittle fracture) Prof. Elices also participates in RILEM TC 147-FMB (Fracture mechanics applications to anchorage and bond) and 148-SSC (Test methods for the strain softening response of concrete). Prof. G. Guinea is the 1994 Robert l'Hermite medallist.
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Rocco, C., Guinea, G.V., Planas, J. et al. Size effect and boundary conditions in the Brazilian test: Experimental verification. Mat. Struct. 32, 210–217 (1999). https://doi.org/10.1007/BF02481517
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DOI: https://doi.org/10.1007/BF02481517