Abstract
A series of uniaxial tension experiments has been conducted to investigate the size effect on strength and fracture energy of quasi brittle materials like concrete and sandstone. This paper focuses on the results of the concrete tests, and specifically deals with the variation of the nominal strength for specimens of six different sizes in a scale range of 1:32. It was found that under given experimental conditions, the nominal strength strongly depended on the specimen size. More important however, is the fact that most of this size effect could be attributed to strain gradients which were present in the cross section of the specimens. These strain gradients were caused by the specimen shape, load eccentricity and material inhomogeneity. Through a combination of experimental data and a simple linear elastic analysis, the importance of strain gradients with respect to the ultimate load level could be visualized. This leads to the conclusion that studying a material size effect is not possible without taking into account structural stress/strain gradients.
Similar content being viewed by others
References
Bažant, Z.P. (1997). Scaling of quasibrittle fracture: asymptotic analysis. International Journal of Fracture 83(1), 19–40.
Bažant, Z.P., Xi, Y. and Reid, S.G. (1991). Statistical size effect in quasi brittle structures: I. Is Weibull theory applicable?. Journal of Engineering Mechanics (ASCE) 117(11), 2609–2622.
Carpinteri, A., Chiaia, B. and Ferro, B. (1994). Multifractal scaling law for the nominal strength variation of concrete structures. Size Effect in Concrete Structures (Edited by M. Mihashi, H. Okamura, and Z. Bažant), 173–185.
Ferro, G. (1994). Effetti di scala sulla resistenza a trazione dei materiali. Ph.D. thesis, Politecnico di Torino (in Italian).
Heilmann, H.G. (1976). Zugspannung und dehnung in unbewehrten betonquerschnitten bei exzentrischer Belastung. In: Deutscher Ausschuss für Stahlbeton, 269, 1–61 (in German).
Hordijk, D.A. (1991). Local Approach to fatigue of concrete. Ph.D. thesis, Delft University of Technology.
Li, Z., Kulkarni, S.M. and Shah, S.P. (1993). New test method for obtaining softening response of unnotched concete specimen under uniaxial tension. Experimental Mechanics (9), 181–188.
Müller, R.K. (1964). Der einfluss der messlänge auf die ergebnisse bei dehnmessungen an beton. Beton (5), 205–208 (in German).
Peterson, R.E. (1974). Stress concentration factors. John Wiley & Sons Ltd.
Sadouki, H. and Van Mier, J.G.M. (1996). Analysis of hygral induced crack growth in multiphase materials. HERON 41(4), 267–286.
Scheidler, D. (1987). Experimentelle und analytische untersuchungen zur wirklichkeitsnahen bestimmung der bruchschnittgrössen unbewehrter betonbauteile unter zugbeanspruchung'. In: Deutscher Ausschuss für Stahlbeton, 379, 1–94 (in German).
Van Mier, J.G.M. (1997). Fracture processes of concrete. CRC Press.
Van Mier, J.G.M., Schlangen, E. and Vervuurt, A. (1995). Lattice type fracture models for concrete. Continuum Models for Materials with Microstructure (Edited by H.-B. Mühlhaus), John Wiley & Sons Ltd., 341–377.
Van Vliet, M.R.A. (1999). Ph.D. thesis, Delft University of Technology (in preparation).
Van Vliet, M.R.A. and Van Mier, J.G.M. (1997a). Concrete behaviour under uniaxial tension: Effect of casting and drying conditions. Brittle Matrix Composites 5 (Edited by A. Brandt, V. Li, and I. Marshall), 329–339.
Van Vliet, M.R.A. and Van Mier, J.G.M. (1997b). Size effect in tensile fracture of concrete: Effect of test-control. Ninth International Conference on Fracture (Edited by R. Ritchie, B. Karihaloo, and Y. Mai), 957–964.
Van Vliet, M.R.A. and Van Mier, J.G.M. (1998). Experimental and numerical investigation of size scale effects in concrete fracture. Material Instabilities in Solids (Edited by R. De Borst and E. Van Der Giessen), John Wiley & Sons Ltd., 185–206.
Vervuurt, A.H.J.M. (1997). Interface fracture in concrete. Ph.D. thesis, Delft University of Technology.
Weibull, W. (1939). A statistical theory of the strength of materials. Royal Swedish Academy of Eng. Sci. Proc. 151, 1–45.
Zech, B. and Wittmann, F.H. (1978). A complex study on the reliability assessment of the containment of a PWR. Part II, Probabilistic approach to describe the behaviour of materials. Nuclear Engineering and Design 48, 563–593.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Van Vliet, M.R., Van Mier, J.G. Effect of strain gradients on the size effect of concrete in uniaxial tension. International Journal of Fracture 95, 195–219 (1999). https://doi.org/10.1023/A:1018652302261
Issue Date:
DOI: https://doi.org/10.1023/A:1018652302261