ABSTRACT
Abstract Causes of size effects on concrete strengths are discussed. An equation for estimating the size-dependent flexural strength of concrete beams with square or circular cross-section is proposed. The distributions of strain on the tension surface of concrete beams were detected with strain gages (gage length: 3, 10, 30 mm). The number of strain-localized portions and the intensity of the localized strain increased with the decrease of the gage length, that is an observation scale. The strains at all portions monotonously increased up to the peak load. The overall averaged strain did not depend on the gage length from the start to the peak load. The possibility is pointed out that the shapes of strain distributions have fractality. Keywords: Concrete, strain localization, crack dispersion, size effect, observation scale, fractal
1 Introduction The knowledge of the size effects on strength and failure behavior of members is important, when designing large scale structures or using new materials. The fictitious crack model proposed by Hillerborg [1] is one of effective concepts to deal with the size effect on strength of concrete members in bending. According to the concept of the fictitious crack model, not only one but plural cracks may propagate in parallel on the tension surface of concrete beams. The possibility of the plural cracks and their effects on the failure behavior have been problems.
